Depth of field and crop factor misconceptions.

[@biscuitsalive]

Hi guys! I just uploaded a FOLLOW UP VIDEO, that handles some criticisms about this video. Also flags a couple of small mistakes i made within this vid. Link- kzbin.info/www/bejne/nHSsiJ6nmMdqfKs

[@DB-nl9xw]

biscuitsalive nice videos, this is how you should learn photography! Please recommend books!

[@unrelatedcomment]

biscuitsalive

[@yongchaozhao8449]

I'm very glad that I learned something from your video. but pardon me. the DOF diagram illustration is showing in your vedio, from my point of view, after the rays refracted through the lens, the focus circle of further object should be on the Focus Plane's left . Because this point circle gives a narrow angle, thus, the rays though the convex lens can give a easy refraction. Therefore, the focus circle should be on the left of the Focus Plane. Hope I can get your feed back. cheers.

[@dmmartindale]

@@yongchaozhao8449 If you mean the magenta dots and lines that appear at about 8:43, you are correct. When the object point moves further from the lens, the image point moves closer to the lens. The video's author does know about the error, and corrected it in his follow-up video.

[@MrVh78]

holy crap! 4 years of film school, numerous shoots, a ton of bro camera science and only now i finally get it, thanks!

[@hawjtsim]

This is the most complete explanation of this yet, been trying to fully understand this for years. Thanks!

[@biscuitsalive]

Billy nice one Billy! Glad it was useful.

[@henrikholst7296]

I had to stop this video now. Not to tell you that "I don't understand what you are talking about", but to say that each time I am to some degree confused, you address the subject and get me right back on track. This has seriously! got to be one of the best informative videos I have ever seen. The hat is off to you, sir! Amazing

[@meme4one]

I have been a photographer for a 5 years now and do a lot of reading and watching on the subject. This is the first time I have had aperture explained to a level where I can understand the mechanics of how this works, not just the effect.

[@biscuitsalive]

Pete B cool! That was my goal. To explain literally what’s happening in your lens as simply as I could. (But still covering a lot of information... it’s a tricky juggle) Be sure to watch my follow up vid. As I did make a couple of minor mistakes in this vid that I wanted to correct.

[@meme4one]

I am an engineer so always want to know the specifics of how something works. I didn’t review the FF vs Crop and ISO parts, as I am always fairly confident in that area. Will look out for the update.

[@biscuitsalive]

here is the link, its a bit boring, but i like to correct my mistakes if possible - kzbin.info/www/bejne/nHSsiJ6nmMdqfKs

[@tristanholmes4153]

Thank you for doing this video. It is hard to find knowledgeable sources for this on the internet. Most people have the “camera for dummies” version of this where it only goes as deep as “iso bigger=brighter” and “aperture smaller number = brighter.” So thank you for explaining the why of it instead of patronizing me with fairly common camera knowledge. 🙏🏻👏👏👏

[@TheArtist441]

One important thing I would add to the video though is the fact that when you shoot full frame, you need to get closer to your subject to get the same subject framing, with everything else being the same. So in your image comparison between the FF and the M43, if you moved in closer with the FF to match the framing of the M43, the DOF would be much smaller in the FF than the M43. This is where people realize that when they shoot bigger subjects like people, and they want an even shallower DOF WITH the same framing, a FF sensor suits them better. And yes, you could use a smaller f number on a lens with a cropped sensor to match the FF in this case, but if you are already shooting f1.8 on a cropped sensor, and want an ever shallower DOF, for the same framing, you will be hard pressed to find a lens f 1 or thereabouts. So the key is keeping the FRAMING the same when comparing FF and cropped with everything else being the same. Fantastic video though, I would have loved to see the differences when getting closer with the FF though.

[@NickWeissMusic]

Moving toward or away from the subject completely changes the field of view and introduces background compression or expansion into the equation. It will absolutely change the framing. If you compensate with a longer lens (multiplied by crop factor) on a full frame, you can achieve the actual exact same field of view as a cropped sensor. Crop sensors are ***not*** reaching further. They are just filling the frame with “more subject,” by cropping out the edges of the full frame equivalent. In the photos at 19:35, if you physically moved closer, you would change the relationship of the foreground and background subjects, changing the framing entirely. But what actually happens if you shoot from the same distance with the same lens, is the crop sensor is just a smaller piece of the larger picture. There are cases where either format can be advantageous, crop sensors do have a pixel density advantage which simulates “reach,” but you are correct that full frame does offer more flexibility with shallow depth of field and light intake assuming equivalent lenses.

[@matthewpeer9396]

This has swayed me to keep my m4\3 cameras and lenses. Great explanation!!

[@biscuitsalive]

Matthew Peer I love both (m43 and FF) Gh4 prob gets most use. But a7s comes out at night. :) Also playing with medium format now too. Fun to tinker.

[@JimberJam]

Thank you so much for this, I've been trying to wrap my head around it for years.

[@biscuitsalive]

Jimber Jam what a perfect comment. Thank you. Let's me know I achieved what I set out to do, and made it nice and clear. :) :) :)

[@JimberJam]

Definitely! I have been shooting exclusively on the GH4, and have gotten a 'feel' over the years, between my native lenses and speedbooster and Canon glass.... but I've never been able to really grasp it, (or explain it to my colleagues who shoot on the FF cameras like the Ursa Mini) and certainly not to explain it to someone else (which is, in my opinion, the true measure of understanding something). Wonderful video, and a happy new sub from us!

[@biscuitsalive]

Thanks! I will have a good nose at your uploads later on tonight. (I subbed, so will catch your new ups too)

[@JimberJam]

:| Don't go back too far! Haha!

[@ZhentianAShen]

Reminds me of the science class on light reflection back in middle school! Thank you so much.

[@c4tubo]

best explanation and diagrams of all these concepts that I have found on YT so far. thanks big time.

[@waynejennings480]

I know this is a few years after this was first posted and am pleased to see someone get it correct, I have been so frustrated with the amount of posts claiming that sensor size changes depth of field, only subject distance, aperture and focal length change depth of field. I do however feel that there is confusion over the ‘circle of confusion’ and I do not see how it impacts the depth of field with sensor size. As you show in you diagram the point of focus is the size of a pixel and a sharp point, reducing sensor size but retaining the resolution creates the overlap onto other pixels. You state that this impacts depth of field, but I disagree, to me the circle of confusion will have the same effect across the whole sensor regardless of depth of field, it has an impact on the overall sharpness and not depth of field.

[@speterlewis]

Excellent. This should (but likely won't) end all the confusion. Math doesn't lie. (And I secretly delight that this vindicates Tony Northrup, who has gotten way too much grief for being right). Thank you for taking the time to put this together!

[@biscuitsalive]

Peter Lewis glad you liked it. :)

[@speterlewis]

@@biscuitsalive Not only did I like it, but I learned a lot from it. Been a working pro for over 30 years, but am still constantly learning things, and your video was so precise and clarifying. Your combination of science, math, and real-world examples was extraordinarily helpful. You're helping to clear the fog away!

[@biscuitsalive]

Peter Lewis nice to hear!

[@VTS-lelovsky.]

Damn, that soldiers analogy... I wonder how physically accurate is it considering the wave form of the light ray. Great video by the way!

[@anglewinder]

This is the clearest, most concise explanation of this subject I have seen. The key elements are succinctly outlined with easy to understand with illustrated explanations. The pacing is appropriate as well without getting overly bogged down in any of the steps. I've seen many videos and read many articles on this, but this video encapsulates these factors the best. Thank you. If I were to offer any suggestion, then I would recommend: 1) Using a larger colored cursor and moving it much less (the excessive cursor movement is very distracting) 2) For the text heavy slides, I would bring in each text section of the slide separately to help lead the watcher digest the information, instead of overwhelming the watcher all at once. With that said, the video is free and offered as a service, so I can't complain too much. I'm very appreciative for your effort and the time you took to produce it. The video is great educational service to anyone interested in the optics of cameras.

[@biscuitsalive]

anglewinder thanks! And I agree on your criticisms. I did this video in one take/recording after drawing the illustrations. I should have spent longer on assembly. But I tend not to put lots of work into KZbin when I’m busy with paid work. KZbin is a fun hobby for me. Nothing more. :) But if I have a quiet work period, you will see spikes in quality on my KZbin content, simply as I then have more time to spend.

[@JACKnJESUS]

Very nice explanation. I have sent several M43 users to your video when they try to tell me their Olympus 300mm f/4 is a 600mm f/4. When I tell them it's a 600mm f/8 and they have to boost the heck out of their ISO to match FF...heads explode. The marketing departments of several camera companies feed off the misinformation out there. Small sensors always pay a price.

[@biscuitsalive]

Yep. They are correct of course when they state their lens/ focal length/Fstops. It’s when they claim their full frame equivalent numbers they often lie on purpose. Some companies even show the full frame equivalence lens next to theirs in the adverts. Not pointing out they the image /depth of field is entirely different.

[@JACKnJESUS]

@@biscuitsalive Why the Engineering depts. always hate the Marketing depts... :P

[@sheslop888]

Well done. I have a hard time getting my head around something until I understand it intellectually. Thanks for that.

[@ldm]

Thanks for doing this video! I've done some FF vs M43 DOF tests and didn't know why the ISO was so different for the same exposure, until now.

[@biscuitsalive]

Nice one Louis, exactly the kind of thing i like to hear. :) (Lets me know I am being helpful)

[@biscuitsalive]

p.s. if you were getting the rest of the equivalence right, and just not the ISO, then you are still doing better than the majority of people I chat to on the Facebook groups... :) They just do the focal length, get bad results, then say the sensor it crap! (doofasus!)

[@fidodido664]

I was looking such a good explanation of dof for many years. Exceptional work. Many "photographers" fill up the KZbin servers with stupid videos and all of them say the same obvious things. Aperture , shuter, iso blahblahblah. You took it the core where it needs to be taken. At some point we need to learn why things happen and how in photography. Great work.

[@sonvfave]

I prefer; " more in focus", and less in focus, as you are correct in one sense there is a thin line in "focus" there always could be theoretically a more shape image .... defined or limited by the medium used.. so in reality there is a " field of focus", which is based on an math equation... or ratio .. which after all is where we get f stop and t stop.. so so much nerdiness here LOVE IT

[@BrianAndersonPhotography]

I am now pointing all my friends that ask me questions about this to your video. This is probably the best lesson on it out of every technical video on KZbin. Thanks so much for taking the time to make it :)

[@biscuitsalive]

Thank Brian. I may well re do this vid to perfect the message (couple of tiny mistakes) but i think it does a pretty good job of combining everything people need to know.

[@BrianAndersonPhotography]

It does a great job. The depth of field discussion alone makes it more than worthwhile. You may not realize this but in the midst of your physics discussion you showed how depth of field works as a tool for the aesthetics of a given photo. Until aperture is seriously understood like this you can end up fiddling around with 100s of photos before you understand it by accident...LOL. The sooner you realize DoF the quicker you can leverage it in your photography. I was one on the people who spent months fiddling with it without this level of understanding. After much trial and error combined with piecing together bits and pieces from KZbin that is actually self-containted in your video, I finally understood it a few years ago. It's so refreshing to have your video on it that it should be posted everywhere. I'm just glad PetaPixel pointed everyone to it. Bravo sir ;)

[@biscuitsalive]

High praise indeed. thank you. I make no bones about the fact I learnt much of this from filmmaker IQ and Tony Northrup. But I wanted to try to combine all of those elements, and also help it be more visually literate with the simple illustrations. (For those of us that don't think in math equations) :)

[@Temersson]

Great stuff, will check the follow up vid, but already a huge thanks for clarifying this complicated subject... been shooting stills for about 25 years (about 10 of those professionally) and only now I have at least a good understanding of the matters (and math) behind all of this! Thank you, Sir!

[@koshobai]

My jaw has dropped to the floor. This answers so many questions. I feel like sleeping after having had a long exam.

[@PostColorGear]

Your information at 20:35 is spot on! I was JUST about to do a video on this. Everyone explains how to calculate the focal length as far as different sensors go, but they ALWAYS forget one factor. Distance. You don't need to make equivalencies if the phone ISN'T composed the same way :)

[@thomasrichardson8327]

Its a real shame that theres content out there that has a fraction of the effort put into it, and get millions of views where this gets just 89,000. A real shame. Youve explained how the aperture works like none other.

[@Koishichan]

I've always liked that analogy about a marching army walking from a hard surface to a soft surface. I think you can take it a step further though. If you imagine each line of people is a different wavelength of light, the higher the wavelength the smaller and faster the gate of those marchers. So all the marchers are marching at the same speed, but on one side you have people taking large slow steps, and on the other side, people taking small fast steps. When they reach the sand, or mud, the people taking big steps get further into the mud before they are slowed down by it, and those taking small steps don't get as far before they are slowed down. That causes the marching lines to diverge from each other. I theory they should begin to converge on the other side of the "lens" but I think that could help explain chromatic aberration.

[@biscuitsalive]

Grant Pluntze nice one! Yep that works lovely. I could see that working in a animation. :)

[@danc2014]

Grant Pluntze Dec

[@massimorodriquez]

wow, wonderful! Just a question. The cropped Iso related to the sensor does it also involve the noise level? In other words, in terms of noise level 800FF is equal to the 200 into 4\3?

[@OutfittersOfArt]

Amazing video. Nice to see someone doing more than just scratching the surface of the subject, but at the same time making it easy to understand what he's saying. Subscribing.

[@biscuitsalive]

Nice to hear, thanks.

[@jonassekondi931]

@@biscuitsalive It's nice to see what's written, or just to read. Hearing that is something else altogether.

[@PhilipZilfo]

This was, put simply, AMAZING! Thanks!!!

[@nysj]

4 years of doubts were explained today. thanks a lot!!! great work

[@biscuitsalive]

:D ... look out for a newer more in-depth version of this coming soon... covering ISO equiv and speedboosters etc with more practical tests to back up the maths. :) (I'm half way through it, but its taking a while as i need to keep finding very specific lenses to do it properly)

[@danncorbit3623]

This is the best explanation I have seen on this topic. Nevertheless, I think it is a mistake to say we make the three adjustments and get equivalence. That's just about as wrong as all the other explanations I see online in one sense. Now, it's true that those three adjustments will make the images very similar. But much of the time it's not even possible to do that. Suppose I use a 85mm f1.2 lens on full frame. Those are common today. Where do you find a f0.6 lens? They don't exist. Let's use an f2.8 100mm lens on full frame. So we need a 50mm lens at f1.4 for mft, which is likely doable. But now, our full frame camera has native ISO of 64. How will we replicate that? And a terrible misunderstanding comes from saying we double the aperture for micro four thirds to get full frame equivalence. That is because aperture is a physical measurement, and using a crop factor multiplication causes another myth because people think that aperture is really halved. But if that were true, we would need to double our exposure. But exposure times are correct. So, while it's true that if we adjust all three of those factors, it's rarely possible to do it in places where it's important. And people often think that statements like "halve the focal length" or "double the exposure" are true stand alone. It is therefore important to explain that these changes are not true when taken one or two at a time and very often they are not achievable. My explanation is that there are ways to make similar images if we intentionally handicap one system or another, but there is not a general way to create equivalence. Sometimes it's the crop sensor with an advantage. Consider a 400mm mft prime lens at f2.8. It has a magnified image so that full frame camera will need a 800mm lens for equivalent field of view. Now it's the full frame lens that can't match because nobody makes an 800mm f4, and if someone did it would be so heavy and expensive that nobody would buy it. True, the bokeh would be different, and there would be more noise. But you could still take pictures in low light because the f2.8 gives real exposure times. Maybe the subject is so complex it can't be made simple, but I have seen a lot of misunderstanding caused by explanations which use all three factors. Don't get me wrong. Your explanation is more clear and correct than any other I have seen. And if we are careful, we can get a correct understanding. But I have seen similar explanations cause as many misunderstandings as the outright myths.

[@PhilUKNet]

Very well explained. I knew a lot of the theory, but didn't know why or how. I think the only subject I didn't know about previously was circles of confusion. Your diagrams really helped. I watched a Tony Northrup video on the same subject recently. What he says is basically the same as you, but he doesn't explain why or how. To do this, the diagrams are essential, which is why your video is a better resource. The subject gets very technical and there's a lot to take in. Some people are very keen on the technical stuff purely for the sake of being technical, whereas I just want to have enough knowledge to help me take photos. I now need to watch the follow up video.

[@klodr]

Excellent video! Great explanation. I found your video looking to more explanations or discussion after the Tony's videos. I simply don't understand why detractors didn't understand or are confused with such basic concepts for a serious photographer. Other interesting aspect is that nobody have provide a single image to show the contrary. Great job.

[@biscuitsalive]

Claudio Rivera thanks! Yes it's crazy why people still argue this stuff. Especially when it's not difficult to spend a hour or so playing with a couple of cameras and see practical results that Back up the theory fairly easily. As I said in my vid I learnt a fair bit from people like Tony N myself, and I wanted to take it a bit further and look at what's happening inside the lens with my little Illustrations. And it's always good to practically test these things yourself to understand things better.

[@shubhkarman4733]

Thank you so much man ! You explained it so well accompanied with perfect examples on the go. There’s so much confusion about this stuff but when you think about it from the mathematical point of view, it all starts to make sense. Cheers dude! Keep up the good work.

[@g4md0r32]

Very nice and easy explanation. The main reason that people say that FF has more bokeh is because the lens for crop sensors are not fast enough to compensate for the crop factor. If they make 25mm f 0.9 with autofocus on MFT it will compete with the standard f 1.8. If they want to compete with the f 1.2 lenses they will have to do some serious engineering to create a lens that has an apperture of f 0.6 . But the speedboosters are a very good solution until they come up with super fast lenses for aps-c and MFT. Let's hope they stop the marketing BS with the crop factors. Best solution I can find to clear the misinformation is to list the focal length as they are but to include the equivalence for the crop factor.

[@CinematicVisar]

Thank you for creating a wonderfully explained and illustrated video on this topic and doing a Follow-Up video. I'm working on a similar video to create more awareness around what makes the IMAX look and why it's not as unique as it was in its digital infancy.

[@eerica860tw]

I have searched for this knowledge for a very long time. Thank you very much!

[@MattScottVisuals]

Wonderful video, thank you :) Just wondering at 25:45, what about distortion? Will the m43 wider lens have different compression / distortion characteristics compared to the 85??

[@Fabio-rg9nv]

Great, now that I got all that, I will get mad at people that say wrong things about it, even professional photographers on KZbin and such 😑. Your fault. Haha seriously now, thanks a lot for that video!! I actually just came across it, wasn‘t searching for it ... but DOF in relation to crop sensors was definitely something I came a cross with a lot! So happy to understand it now! :)

[@biscuitsalive]

Fabio Mota glad it was useful. :)

[@SidLives]

Thanks for taking the time for putting this together, got my first DSLR recently (I’ve only ever used compacts) and really disappointed the sales guy didn’t explain about the cropped sensor vs full frame, and, I can’t understand why Canon won’t label the EFS series of Lenses what they actually are considering they can’t be used on the FF, after watching this video and Tony Northrup I’m now getting better exposure with my pics

[@biscuitsalive]

rawknroll Paul glad it was useful. Yep a system that shows the FOV angle and the total amount of light let through would be much better than focal length and fstop

[@MrBooojangles]

I get it, but I'm trying to find out why my Canon 80D with 18-135 kit lens doesn't have a big depth of field when I have zoomed out. I was suspicious of it not doing this over the last year, so yesterday I did a DOF test on a long row of railings posts, so I compress them by zooming out. I first stood close to them and did around a 60mm focal length, I focussed a third of the distance in to the shot and tried at f8, f11, f16, f20. I know you get refraction with this lens after f11, but it was a DOF test and I still couldn't get everything in focus front to back. It did improve, but still the near and far posts were blurred. I then went around 24ft away from the end post I was stood by and zoomed to around 125 or 130mm and still had the same problem. I thought at least by f11 or f13 everything would be in focus. Is this a fault of this lens, or is this normal, do I have to crop photos every time, or am I doing something wrong. Does this happen with every lens on a Canon crop sensor, because at the moment I can get bigger DOF on my old bridge camera with a tiny sensor, zoomed out at f8. One reason I went to a DSLR was for its much bigger range of aperture values and being able to get everything in focus when I wanted that.

[@bencushwa8902]

50mm (for a full frame lens) is roughly a "sweet spot" in terms of front element size. Assuming you keep the aperture the same, at shorter focal lengths you need a larger front element to accommodate the wider field of view, and at longer focal lengths you need a larger front element to accommodate the larger physical aperture size. Physics is fun! :)

[@Stephen.Bingham]

I think these discussions are much clearer if we focus - no pun intended - on the lens rather than the sensor. The light gathering power of a camera, and its ability to render a shallow depth of field, are determined by the area of the lens’ entrance aperture, and not the sensor size at all. For a fixed depth of field, smaller sensor camera operate at numerically smaller f-stops and iso values - the total amount of light hitting the sensor is independent of the sensor size - and the image noise is typically very similar.

[@livetcell]

I loved this video, finally someone took the time to explain this in a way I can understand. I have a question concerning native mft lenses. So say you have a 25mm 1.7 prime. That would be 50mm on full frame, but do you double the aperture of native mft lenses as well?

[@biscuitsalive]

Daniel Strauss thanks. That's what I was going for. Explaining it a bit more visually (illustrations etc) Yes. That's exactly what you do. So a 25mm f1.7 M43 lens will perform just as a 50mm f3.4 lens on full frame. This is why we need really fast lenses on M43 if we want to match the DOF and image noise quality of FF. My fastest M43 lens is a 42.5mm f1.2 And that works exactly like a 85mm f2.4 (Lovely for portraits) Or as you probably already know, u can use a speed booster and this gets you most of the way there, and use the same lens as you would on the FF. (But with a slightly tighter shot)

[@biscuitsalive]

Daniel Strauss just a side note on this. When you get a native crop sensor lens that completely matches the performance of a FF lens. It will have to be as physically big as the FF equivalent. (Front element has to be big to let in enough light etc. ) So you can practically just eye ball the crop sensor lenses and tell. This is why it's outrageous when a manufacturer states something like. "24-300mm f4 equivalent" on the lens or fixed lens crop camera advertising/description. When it's a actually a 12-150mm f4 M43 lens. They should have said "24-300mm f8 equivalent." Then they wouldn't have been lying fiends! ;)

[@livetcell]

Thank you! I get it now. Yeah speedboosters help a great deal in achieving that full frame look on mft.

[@robbyboyo]

I watched the mistake film first. A very good real world set of examples.

[@biscuitsalive]

robbyboyo cheers Robby.

[@haiderabbas96]

Great video and excellent explanation. Wish you would have mentioned the lens compression too :). According my understanding it totally depends on the physical distance between the camera and the subject, therefore on an equivalent of 85mm (56mm or so) on crop body the compression would be same as on a real 85mm on full frame body. Please let me know if I am missing something.

[@biscuitsalive]

Haider Abbas I was just thinking that last night! (That I should have mentioned compression) Yes, although I haven't tested for that personally yet. (Always like to test things physically before accepting anything fully.) I agree that it's just down to distance from subject. Makes sense and it's just the relationship between one object overlapping another from a line of sight. And the FOV of course. As you get further away from the subject. (Say an actor) but the FOV angle shrinks. (To keep framing the same on that actor) So we see less and less of the background scene. And the actor is also actually covering less and less of that background. (Not as important, but worth noting.) This obviously does the same thing to everything that is at difference distances from the camera. (This is why face distorts when using very wides lens, up close. And the same face looks flattened and more orthographic from a great distance with a very long lens. ) Anyway, good point you made. There's a good chance I will revisit this topic again in a future vid, as I have learnt a lot from all the feedback I got from everyone. Both about things I should have said. And ways to make the trickier parts even more clear. Not to mention I would like to add some raw independently gathered data that further proves some of the still disputed statements. (By a small but very vocal minority.) :)

[@rx58000]

2:14 why would the image be focused to singular point rather than whole sensor ? I feel this question is stupid be I would like to know

[@biscuitsalive]

Think of it this way. Every point in the focusing plane in the real world, is focused down to one point on the sensor. As you watch further that is illustrated

[@evasabzacami]

Thanks for the video, very informative. There is only one question that I don’t understand completely. That is how to achieve the same amount of exposure, DOF and NOISE. It is clear why you need to lower the ISO by the square of the crop factor - increasing aperture from 4 to 2 is exactly 2 stops, decreasing ISO from 800 to 200 is also 2 stops (the same would work if one were to decrease the exposure using SS). What I don’t understand is the fact that noise will be the same. If we have 2 sensors with the same amount of pixels, say iso 12800/22750 on M4.3/APS-C should definitely look cleaner than iso 51200 on FF. At least this is what I experienced with my Sony A6500 vs Sony A7IV. Could you please elaborate on this?

[@voodoo9325]

Simply brilliant video. No fancy bullshit and down to the point.

[@biscuitsalive]

Thanks for the feedback, be sure to check the follow up, couple minor mistakes in my illustration which i dress there.

[@howardmaryon-davis666]

Very good explanation, thank you for clearing up some misconceptions. The most contentious issue for most will be the noise/iso relationship which will upset a lot of m4/3 and some aps-c owners. You need very much faster lenses to keep the sensor noise under control. As you say, manufacturers are realising that they have to be more honest about lens equivalence not only focal length but also max aperture. Camera and lens manufacturers should make speed boosters that are specific to their larger format lens ranges. I.e. Fujishould make one specifically for mounting full frame legacy Fuji lenses on their aps-c camera bodies.

[@biscuitsalive]

Howard Maryon-Davis I agree. And the point about the noise vs sensor size has the most variables to factor in. (In regards to each sensor technology/design etc) But I believe it’s safe to say if you took two identical sensors (in terms of the technology, eg. Back lit/cmos/ Same res etc etc) but one is smaller than the other. Then you can use the crop factor squared to equate noise levels. (across the whole image. Bare in mind if res between sensors is different, and you judge image noise at 100% then the formula brakes down as the portion of total Sensor is no longer equal. ) This is why judging 2 x 4k full width sensor images is a good/fair test to reference. As even if one sensor is higher res. The down sampling to 4k helps even things up. (As long as using whole width of each sensor and not cropping like the gh4 does)

[@juliusherrmann7222]

quick question: Is the hurdle a lower base iso, or higher base iso? Would have guessed the iso is already higher, being equivalent to a high ff iso. Correct me if I am wrong. Great video.

[@biscuitsalive]

Julius Herrmann the hurdle for smaller sensors in optimum conditions is lower base ISO. To match image noise of full frame camera at ISO100 a m43 needs to be at ISO50 at most. But new sensor tech will no doubt change all this soon. But there is always going to be an advantage to larger sensors. Most noticeably in bad light /high ISO range.

[@traianivanescu24]

Thank you for this video. You nailed it. Thank you for mentioning Filmmaker IQ. It's great. Thank you for the reference.

[@biscuitsalive]

I just want to say thanks for the engagement on this video folks! Apart from a very 'shouty' minority on the forums. Most people get it and agree. I think the really clued up viewers already knew this stuff anyway, but I think also a fair chunk of you learned something useful. In which case Im glad the video did its job. And I would like to again remind you to check out Tony Northrups, and FilmmakerIQ channels. As I myself learnt a great deal from them, and hopefully wrapped it all up for you into this one vid for you.

[@yourtallness]

I've seen Tony's take on this and the current video which largely corroborates the same points. It makes sense to me that total light captured is important since we are blowing up pictures to the same display medium (screen or print). It seems like common sense to assume that the light 'wasted' by the cropped sensor not capitalizing on the full image circle projected by the lens would incur a penalty since we are losing "optical resolution". One thing that does intrigue me about the Angry Photographer's take on this is that he insists it is wrong to assume that bigger sensors are like bigger solar panels and consequently no penalty actually exists for cropping (does this mean that the part of the image circle that is captured still yields vastly greater optical resolution than the photosites available to capture it and "wasting" light by cropping stills leaves plentiful optical resolution anyway? - I'm confused...). Angry's point is also that a lens does not care what sensor lies behind it, but I don't think either Tony or biscuits contradict that statement. It would be nice to have them openly debate about this. :-)

[@biscuitsalive]

Mark Pitsilos it seems to me you get everything you need to know to understand all of the major points in the vid. I'm kind of too tired now tonight to give any any more feedback regarding the some of the minutiae side details. So il leave it there, and pick up any remaining loose threads tomorrow eve..... Night!

[@biscuitsalive]

just skimming the comments again, regarding that angry guys take on it, I'm confused as hell by his comments, he keeps changing his mind as to exactly what is wrong with the points in my video. And once i realised he was unhinged i have now ceased all communication with him and blocked him on every platform he shouts and spits nonsense in. :) (one of the biggest nutters i have EVER met online. without a close second, he spammed me with so much crap you would not believe it.) but regarding the 'not working like solar panels' argument. This makes no sense to me. The only way his argument would hold any water at all is if, when a manufacturer scales up the sensor size from one type to another, they keep the actual photosites the same size, (now with each 'pixel' having a tiny gap around it). But obviously they don't do that, because they want their sensor to be as efficient as possible. so they cram as much light sensitive surface area into the sensor as possible, wether its big OR small. the signal to noise ratio is what its all about. just like in audio, if you have a weak input and add a ton of gain you get crappy results. (the noise floor is raised etc.) A image sensor simply needs as many photons as possible to give us that strong SNR. and when you make the blooming sensor smaller, it has less photons hitting it.... like, no sh*t sherlock. Even a child could see this as perfectly logical. And considering all of the DXOmark testing data, and all of the practical experience from anyone that uses several sensors sized cameras will tell you. the sensor size has a DIRECT relationship to image noise. As you probably already saw from TonyN vid- 'Crop Factor 4: Debate with a Critic & New Sensor Performance Data' The sensor size has way more sway on image noise than even technology improvements over a few years span. And even when you compare the very worst performing camera to the very best in a particular year. Size still wins that particular arm wrestle time and time again. So why he (angry fat dude camera guy theo or whatever his name is) can't see the wood for the trees despite everyone around him pointing to the mighty oaks all around him and telling him he's in a forest I have no idea. :)

[@Noam_Kinrot]

Firstly - thanks for the detailed explanation - 1 point about FF vs. APSC (or MC43), is the recent shift to cropped sensors with high count of MP, i.e., emerging 33MP APSC cameras rumored to come out the next few years - I would like to see this video updated to include the effect of such a shift (more noise - since less light per pixel, but maybe compensated since it makes a difference to the coverage of the CoC ? - And if so,is it pronounced enough to nullify the effect? -Under "low light"/ Normal Light ?

[@janmyskowski1204]

Am I correct that the crop sensor lens manufacturers also omit the angle of view differential when presenting 35mm equivalent data? Superb video. Thank you so much for producing it.

[@biscuitsalive]

Jan Myskowski thanks. They vary from manufacturer to manufacturer. There is nothing wrong of course to stating a full frame focal length equivalent, on a crop lens/camera. (25mm m43 saying “50mm equiv”) But to state that, and then state the NATIVE fstop is massively misleading. Either don’t put any FF equivalent. Or put both FL equiv and Fstop equiv. You see adverts and they say on a M43 14-140mm f3.5-f5.6 lens-> EQUIVALENT 28mm - 300mm f3.5-f5.6!!!! It’s not! it’s equivalent to a 28mm- 300mm f7-f11.2 Anyway. You get the idea. They use incorrect maths to confuse people. Then this is why consumers sometimes are disappointed in the performance of their crop sensor gear. It’s not the equipment. It’s the lack of awareness. Unfortunately. If you want full full frame performance on a crop sensor then you need fast enough high quality lenses. (Which do end up being nearly as big and heavy as the full frame counterpart. :/ )

[@janmyskowski1204]

Really appreciate your reply. What I meant to ask, and probably did not word clearly, is whether you need to account for the fact that a given focal length has a fixed angle of view. You can say that a 50mm APSC lens would have a FF equivalent focal length of 75mm or so, but it still has an angle of view of 44 degrees or so, whereas a native 75mm FF lens would have a much narrower angle of view.

[@janmyskowski1204]

I just watched your terrific follow up video. I’m not sure whether I am more confused or less confused about this question I am posing!! You are using the term field of view and I am using the term angle of view. Your last diagram in the follow up video shows that the field of view changes when putting a native FF lens on a crop sensor camera. My question is whether the angle of view stays the same? Angle of view seems to me to be a constant of the glass. If that is so, it seems to me that you would get a different “look” between the otherwise identical fields of view. Or, maybe I just have my head up my ass. Help!

[@biscuitsalive]

Jan Myskowski field of view and angle of view are the same thing. Yes the angle of view is same for lens. But when you put smaller sensor behind it the full image circle (created by lens) isn’t used. Smaller the sensor the narrower the angle of view. (So on m43 the angle is halved compared to full frame. Hence the “2X crop factor” ) Hope that helps.

[@janmyskowski1204]

Thank you!

[@eoinmm]

also - when talking about DOF being slimmer on an m43 lens, how are you calculating your math there? I was always taught depth of field is related to: focal lenght, aperture, snesor/film size and then obviously distance to subject. is there some shift in the math now that you're going from photochemical to pixel? or were you speaking just in terms of using FF equivalent numbers in regards to focal lengths?

[@2516killer]

This is one of the best explanation video I have ever watched. Nice job and thank you !

[@biscuitsalive]

glad it helped :)

[@iamakkkshay]

Thank you very much for this video. You have opened my eyes and brain.

[@ChristopherBurress]

From my understanding the focal length is measured from the convergence point not sensor plane to the lens element. Correct?

[@biscuitsalive]

when the lens is focused at infinity, and its in focus, then the FL is the distance to the sensor, but yes technically its the distance to the lights converging point. (if there was no sensor there to project an image onto, then it would still have a focus length...)

[@biscuitsalive]

of course I'm assuming the set up is correct with the way i described it, if you put a FF lens straight onto a m43 body with no adaptor, and the converging point was throwing behind the sensor, then the FL wouldnt be measured to the sensor... but then you couldn't use this set up anyway. :)

[@ChristopherBurress]

biscuitsalive biscuitsalive well the convergence point isn't necessarily the focal point. Otherwise as images came in and out of focus they would flip upside down and right side up again. The convergence point is where all of the light crosses and flips over. Let me re-watch the video and pay closer attention (in 35 min you can get distracted lol) then I'll return to the comments here. I did a similar video about crop factors. Maybe check it out and we can discuss.

[@biscuitsalive]

not it wouldn't flip, all light throwing off back of lens is in lines that describe the image, upside down, if you skip to around 08:48 you can see what i mean, the OOF areas are not then flipping back up the other way, if you move the sensor nearer if just gets blurry, if you move it further away it gets blurry too. it doesn't also flip from upside down to right way up..... i think you are getting the rays that trace points of light (for one tiny bit of detail) mixed up with the entire image. its the tiny points of light that are converging to create a 'IN FOCUS' image... the entire image will be upside down any way, in focus or not. il have a look at your vid later on. :)

[@ChristopherBurress]

This might end up as spam because of the link. But this is how i understood focal length to be measure. expertphotography.com/understand-focal-length-4-easy-steps/

[@konczpeter76]

biscuitsalive: Thank you for your comprehensive and useful video. I knew about the DoF and aperture correlation, but with different sensore type it seems to be a complicated concept. So I felt this, but I’ve never put this together. Now i understand better how it works. I would have 2 questions, and i I know this information is in your video, but really just would like to make sure if i get this right. I am asking this from an APS sensor user point of view. For me having a nice background blur on a portrait image is the most important. 1, fuji fx has 1.5 crop factor. If I would like to have the same blur than I have with nikon FF 50mm f1.2, I would need 35mm f0.8. There is no such lens on the market. Right ? Only thing I can do that I use a longer lens and step backward. Am I right ? 2, ISO has nothing to do with other feature of the image except noise level, isn’t it ? I am just asking because I am an APS user now. In order to get similar nose than I got with nikon on 100 ISO, I would need 44 ISO on Fujifilm APS. Again, there is no such sensor. So I guess the main differences show at the “lower end” of the parameter scale. On the other hand there are noise level differences between different type and brand of sensors. So ISO 400 dosn’t result the same level of noise e.g. sony and fuij APS. The noise is not only matter of size. Right?

[@rowanlacey5191]

Very useful video, thanks! Learned a bunch of stuff I'd no idea about before :)

[@biscuitsalive]

Rowan Lacey really appreciate that. With such a contentious and potentially confusing topic, positive comments/feedback really are useful to hear. Then I know I made it all nice and clear. :)

[@glasairdriver]

This is a wonderful video. I now understand the physics behind applying the crop factor to focal length and aperture. However, I don't understand the physics behind applying the applying the crop factor squared to the ISO other than it is an area rather than linear. First, I assume I could decrease the shutter speed by say two stops rather than increasing the ISO by two stops. Is that correct? Second, what happens if the full frame is 50mp and the ASP-C is 24mp? It seems the crop factor should be applied to the focal length but now it is less clear what I should do to aperture and ISO. biscuitsalive, I would appreciate your comments.

[@biscuitsalive]

Thanks. Yep it is a bit confusing. So what I’m getting at regarding applying crop factor squared to the ISO is that then completed the full equivalence. So CF to focal length makes FOV the same. CF to aperture makes DOF the same. CF2 to the iso then makes exposure match. As you’ve closed down the aperture on the full frame camera we are getting less light in the camera. So you have to up the iso to match exposure. And remember it’s surface area we are talking about. As the FF sensor is 4 times the area of the mft sensor. So if each pixel is to be getting hit by the same intensity of light (across the whole area) then you need 4x the light falling across the whole sensor. (Imagine if you took a magnifying glass and focused the light down onto a smaller area. It’s the same total light entering the glass. But it’s focused down into a smaller area. This is kind of what we need to do.) The thing that confuses everyone is they think of ISO as a “sensitivity” but it’s not really it’s gain. And that gain is calculated per square inch (sort of). So iso 400 on a small sensor isn’t really the same as iso 400 on a big sensor. Iso 200 on a m43 sensor is technically more like iso 800 on a FF sensor. This is why it all fits together perfectly when you follow my full equivalence. Because (to answer your second question too) when both sensors are THE SAME RES. The. And both technologies are about equal. The FF at iso 800 will have same image nose as a m43 at iso 200. So yes if one has completely different res this does completely change everything. Just as if 2 camera with identical sized sensors has one high res and one low res. Generally speaking the lower res camera has less noise. But again this is debatable too. If you took 2 FF cameras one 52mp and one 12mp (same technology just diff MP) Then if you looked at a 100x100 pixel area of both the low res sensor would be much cleaner. BUT if you looked at the entire image. From the same distance. Chances are image noise would be very similar. (Some small advantage to lower res sensor due to packing in less technology into small space) So this is the thing. For me who generally shoots video. And nearly always at 4K The lower res sensors. (Like a7s2 Or gh5s) has the best chance of low noise. But for photographers it’s a bit debatable. Pixel per pixel lower res sensors have less noise than higher res. BUT THIS IS JUST BECAUSE THE ACTUAL INDIVIDUAL PIXEL (photosite) IS LARGER. Sorry to shout. Just that’s something that many people argue about so I feel it need capitals to drill the point home to any of those guys that may be reading this. :D

[@glasairdriver]

Wow. I appreciate your fast and detailed response. Thanks. I take a lot of bird photos in the wild with my Canon 80D and was considering the Canon 5DS. Using the same 400mm lens, the 5DS could possibly give me comperable bird photos but then dynamite full frame photos for landscape, etc. Probably not worth the price and the slower frame rate. Thanks again.

[@biscuitsalive]

glasairdriver no probs. Hope my response made sense. Often type faster than my brain. :) I’m still loving my Sony a7iii for stills at moment. (With canon/sigma lenses) But I’m more of a video guy than a stills guy. Anyway. Happy snapping.

[@karkrash81]

best vid i've seen on this so far. great job!

[@biscuitsalive]

Thanks William, glad it ticked a few boxes for you :)

[@mahidaparthsinh9386]

Thanks i learned a lot from this video! Thank you!

[@privatebydesign1808]

At 17:00, the difference between sensor size accounting for the shallower dof on a smaller sensor has nothing to do with pixel size. The difference is because for a relevant comparison (same sized output) the smaller sensor output is magnified more, ergo it demands a smaller coc on the sensor to attain the same output size/coc relationship. Pixel size has nothing to do with any of this, nothing at all. Magnification, and the fact that you need to magnify a smaller sensor output more than a larger sensor has everything to do with it.

[@biscuitsalive]

Scott Ferris I sort of agree with you. It's not about the pixels really, but I was using a few pixels simply as an example as to why the CoC could be considered OUT of focus on one sensor, and IN focus on another (even with exactly the same lens, same aperture, same distance to subject. ) Let's forget resolution differences between the sensors, and say we are filming 4K video on both sensors. (More like how I would use them in practice anyway) The 4K on the crop sensor obviously has narrower tolerances for what is acceptably in focus ,and what is acceptably out of focus. Due to the CoC. So that's why I used the pixels to explain the difference. (Personally I thought it was a nice clear way to show this. But obviously you disagree.) Anyway I don't think you are arguing with the overall point I was making at all. You just don't like the way I expressed my point.

[@privatebydesign1808]

Of course you agree, my comment is accurate :-) I understand what you were doing, the problem I saw was you never mentioned magnification differences, which is absolutely key to understanding the differences we see, and presented that issue in the terms of pixel size, that will lead to confusion and inaccurate understanding of your otherwise excellent video. The site that explains it all in as much detail as you could ever wish for is here www.josephjamesphotography.com/equivalence/ I am definitely not arguing with your point, just hoping you could add an addendum to point out that critical element of the equation. The magnification 'thing' is so fundamental to photography, and is never talked about, how many people acknowledge or understand that when you crop an image and view at the same size you lose DOF? Once you understand that getting f1.0 dof in your portraits isn't difficult or expensive, just maths :-)

[@biscuitsalive]

Scott Ferris I think the fact I shrunk the sensor down does clearly show the magnification. (Just sort of inverted) Anyway. Glad you agree in principle. Certainly there are ways I could have described some of this better. I really should have wrote a script. But decided just to reasearch the facts for a few days. Then start recording. :) Clearly not the best way, but it's the quickest. (One take wonder)

[@biscuitsalive]

Scott Ferris I may make a "proper" version. With tighter structure and fully animated illustrations. (Less power point like :D ) If I have time of course. Probably a weeks work to do a high production value version. So I'm calling this one the alpha version. :)

[@privatebydesign1808]

To be sure, the only reason I made an account and posted for the first time ever is because you specifically ask people to at the end of your video. Not emphasizing the fundamental nature and impact that magnification has in an equivalence explanation is an omission of some note. I applaud your video, and your need for tea at the end :-) but wish, very much, you had included that element.

[@ericlowenbach5151]

I always think about DOF as subject magnification (distance to subject and focal length) plus aperture. For instance, macro has very low depth of field because subject magnification is higher than if you were say, fitting an entire elephant on the sensor. If you are fitting an entire mountain range on the sensor, subject magnification is very low and depth of field is correspondingly very high, no matter the aperture.

[@eoinmm]

in your tests you said both ff and m43 sensors were using "native lenses' - which tells me if you're at 50mm on both (50mm ff and 50mm m43), the m43 FF equivalent would be 25mm, right? my main question is regarding aperture - the lens manufacturers have already given us the m43 focal length on our 25mm (and sometimes will advertise their FF equivalence), do they THEN need to also give us adjust aperture readings (t stops versus f?)

[@okaro6595]

A focal length is a focal length. It does not matter what the format is.

[@KoopmanCoaching]

Fantastic video! I enjoyed the follow up as well. I have a quick ? on the circle of confusion and how it effects the other metrics when you take into account when sensor sizes scale, the resolution often changes as well. For instance a GH5 vs an A7RIII.

[@biscuitsalive]

TheKoop117 yes in this video I was mostly talking about same res at diff sensor sizes. (So 4k video as I mostly use) Higher the pixel density the smaller the circle of confusion becomes. But in terms of end product it still comes down to how it’s viewed. If it’s printed huge and viewed close the allergens depth of field will become narrower. And visa versa. So you do need to take into account the circle of confusion of the sensor/pixel density. AND the final viewing set up. (Tv screen at 3 meters... cinema at 20 meters... billboard at 50 meters etc)

[@VeebenCharlie]

Hats off bro! Nice and concise. Keep it up. Need more info like this.

[@Alex-fk3ni]

Well, smaller pixels do not give shallower depth of field, because the circle of confusion stays the same. We just use more smaller pixels to show the same size of that circle. I mean if the circle of confusion has diameter ~0.02 mm, it doesn't matter how many pixels we use to show that point (1 pixel with diameter 0.02 mm or 10 pixels with diameter 0.002 mm).

[@andrewrankin4011]

Okay so I have a question. After you applied the crop factor to the aperture, you ended up with the full frame image at f4 and the m 4/3 at f2. So of course these images look the same now. But with the full frame you still have the option to go to a lower aperture as opposed to the m 4/3 image you are at the lowest aperture setting (generally speaking if using a zoom). With that in mind wouldn't the full frame then be giving you a better depth of field?

[@insanejughead]

29:20 of the​ video he explains that consumers are wanting lens makers to offer true equivalent lens options. But, I understand that Canon's famous 50mm f:1.4 is going to be hard to replicate into a 32mm f:0.875 for my APS-C Canon M... or a 25mm f:0.7 for a M4/3.

[@JACKnJESUS]

Yes, FF wins. Makes sense though. Bigger is better. Always has been, always will. If you know what you are doing that is.

[@belok177]

Does this apply also to the opposite - to get deeper DOF on a crop sensor I can use more open aperture?

[@TheVirtualTim]

I did catch a few mistakes (you had a few drawings with light bending in a way that would not really happen) but overall this is nicely done. When light passes through a lens element, the lens element does not "know" what is behind it. It doesn't know if it's a big sensor or small sensor. The physics of the lens has the luxury of ignoring the sensor size. Another way to think of it is if you have a slide projector and a projection screen, you can swap a large projection screen for a smaller projection screen. The "projector" does not "know" you did this. But of course the human... DOES know. So the human reacts to the change by adjusting the projector... either changing the physical distance so the image "fits" the screen... or perhaps the projector has a zoom lens and we can adjust the focal length. Basically the short of it is... the actual DoF doesn't _really_ change (strictly in terms of laws of physics)... but the human reaction to the new sensor size (to achieve an equivalent framing) causes the photographer to do things that DO impact the DoF.

[@biscuitsalive]

hey, thanks, not sure if you watched the follow up vid too, i did flag a couple of silly mistakes in that. (my light ray vectors did go the wrong way at one point) but it doesn't change the overall message, just a silly mistake with my simple illustration. anyway, thanks for input.

[@mabelbohms4764]

Amazing explaind! I`ve a question :) Do you know or there are some formulas to calculate this different factors or put them together? (And then especially with the sensor size itself)

[@daaknait]

You are the only source on the internet that I've found to explain these things in this amount of detail. Amazing! I was looking for exactly this for weeks!

[@darlingtoncd]

Good video and explanations, but I felt that @24:00 the FF should be at the same settings f2 & ISO 200 (

[@biscuitsalive]

darlingtoncd thanks. There was a couple of minor mistakes. I did a follow up vid to clarify those. (But doesn't change main results) :)

[@darlingtoncd]

Having really looked into this hard. I have to say the settings: M4T == f2 --- ISO 200 --- SS 1/40 FF == f4 --- ISO 800 --- SS 1/40 (f2 --- ISO 200 ---SS 1/40 [2 stop adjustments to maintain exposure]) To apply the crop factor (from the FF ) FF == f2 --- ISO 200 --- SS 1/40 M4T == f4 --- (f4 is the crop factor applied to the FF aperture which would be the M4T depth of field equivalent to the FF but not actually setting the FF TO f4. There's an on-line depth-of field simulator which will further confirm this) Filmaker IQ channel shows this and the only thing that may bring the M4T up to, or near the FF, is the use of a speedbooster. It's horses for courses, the FF shooting at f1.2 (£1700 lens) and ISO 100 etc etc that's what FF can do, at the extreme use of shallow depth-of-field settings, that's simply what the FF can achieve . On the other side; that greater depth of field from the smaller sensors have their value when you don't need/want/desire the extreme shallow depth of field, which is certainly not needed all the time. In a run and gun use of either sensor size the use of the camera and settings is open to what the photographer / videographer wants. There is an over lap in achieving similar/same results, it's just at the extreme settings, that's what those cameras can do. I didn't want to make too much of this but I can't ignore what I see and realize the settings results. I can always discuss further and hope to create a chart to break this down in a, visual form ...I'll have to give that some thought first. I'm pretty sure this is right and will continue to break this down, as you say a lot of people are confused by this and I seem to think I've got this right.

[@zsh6986]

Everything is very logically and well said, but I do have a question. Why does the total amount of light determine image noise, not the amount of light per square inch, assuming the sensor technology is the same? It is very tempting for me to think if the amount of light per pixel is the same (assuming pixel size is the same), then the noise is the same.

[@biscuitsalive]

Shanghao Zhong I think you missed the point slightly. It IS the amount of light hitting each pixels that matters. The main point about the "total" light is that when the sensor is smaller the ISO is still measured by square unit. So, for example, let's say a bigger sensor and a smaller sensor has the same resolution. The lager sensor is getting more light hitting each pixel at the same ISO number. Because of the way they measure sensitivity and exposure. This is why it better to consider the total light rather than how much is hitting a portion of the sensor. (Square unit e.g. a square mm) Simply because the larger sensor will have more of those units than the small sensor. It's the way it's measured is the problem. And we are concerned with ALL the light that makes our image. (More light = stronger signal to noise ratio) It's the image that matters. Not the arbitrary way ISO is measured. ISO is very useful if all sensors are the same size. But basically lies to us when comparing different sizes sensors.

[@zsh6986]

Got u. You are assuming resolution are the same (e.g. a 40MP FF vs 40MP M43) while I am assuming the pixel density is the same (e.g. 40MP FF vs 10MP M43).

[@biscuitsalive]

pretty much, although I'm more coming from video, so you would be shooting 4k (or 1080) for any sensor size. so the end res is the same regardless of the MP of the sensor.

[@alexstevensen4292]

If you scale down a hires picture to a lowres one then you also reduce the noise. Noise is most in the HF component. Say you compare two sensors of the same size same everything except pixel density, the higher resolution one will have a higher noise per pixel but if you scale the resolution down afterwards to the lower one the image will have the same amount of noise. (more or less there is some difference I guess). Also if you take a large sensor/lens combination and scale the result down afterwards you get a better noise ratio. It's really the total amount of light that matters. If you turn this around and take a very small lens and very small sensor say 100x100 if you take a picture with that and blow it up full size you get awful noise. The bigger the sensor (assuming the same light per square inch) the more the noise gets pushed away into details.

[@alexstevensen4292]

Short version of this yes noise is the same but noise is in the details, in the high frequency part of the picture if you 'zoom out' it gets less and less. Noise is not just spread all over the frequency spectrum.

[@sonvfave]

and finally for those new like myself I use the highlight in focus area feature, different names per manufacturer. and then adjust the aperture and watch the field change... Its easier now after a year with this to mentally imagine a wider or narrower dof.... good luck all...

[@yongchaozhao8449]

I'm very glad that I learned something from your video. but pardon me. the DOF diagram illustration is showing in your vedio, from my point of view, after the rays refracted through the lens, the focus circle of further object should be on the Focus Plane's left . Because this point circle gives a narrow angle, thus, the rays though the convex lens can give a easy refraction. Therefore, the focus circle should be on the left of the Focus Plane. Hope I can get your feed back. cheers.

[@biscuitsalive]

Yongchao Zhao watch my follow up video. In that I pointed out a couple of minor mistakes that I made. I think that answers your question. (Although I’m not certain as the message was slightly confusing.) Thanks.

[@Sameir8055]

Thank you so much... Mistakes are spotted :). But, thank you so much for this detailed explanation.

[@biscuitsalive]

Sameir Ali thank you Sameir. Which mistakes? (Want to add annotations for any to keep the wolves at bay.) I misspoke a couple of tiny times. (Saying complete when I meant compete near end etc.) But I think it's still fairly clear what I meant. But please do point out any specific mistakes so I can amend.

[@biscuitsalive]

Sameir Ali and I would redo some of the illustrations slightly. (Apple too close to end of lens, and this muddied water for certain points.) Also, the DOF area (yellow dotted line) should be stretching out so more area for "acceptably" in focus behind focus plane then in front. But again that doesn't change the core message... but I should have factored that in.

[@Sameir8055]

All the mistakes are acceptable and understandable. By the way, I think you said about square of 200 is 800, that needs to be corrected. What you said about the crop factor was right. So, the ISO is not be be squared. It should be multiplied with 4.

[@Sameir8055]

I have subscribed to the channel, and keep looking for more information. Keep up the good work.

[@biscuitsalive]

Sameir Ali no what I said was we square the crop factor for the ISO (I will re watch to check I said it correctly later... but certainly that's how I wrote it down for the illustration) So our crop factor for the M43 to FF is X2 So if you get your calculator out and type out, 200 times 2 then press the squared button. This gives us 800 If it was APSC it would be X1.5 (canon is 1.6) So 200 times 1.5 squared = 450 So ISO200 on a apsc cam. And ISO450 on a FF would equal the same total light. And have equivalent noise.

[@djuydoiu2627]

the output of the lens at the back of the lens ? whats if you not have the same lens with a different output size ? good video very well explained

[@dimitarkaramanov8722]

Great video. Only for ISO is correct but if m43 camera is 10 mpx and FF is 40 mpx that the ISO is the same (pixels per sq. inch). If the resolution is the same, you have to multiply by 4 (2 x 2). For that m43 limit now is 20 mpx (they can not support more for ISO)

[@biscuitsalive]

Regarding MP. I work in video. So most of my calculations are presuming we are looking at 2 cameras at same resolution. (Both shooting 4K )

[@danielemorabito2357]

I have a question, what about perspective distortion? I mean, by applying the formula you get two images equal in terms of fov and dop but the perspective of 85mm shall be always different from a 42,5mm? Am I getting something wrong?

[@biscuitsalive]

are you talking about lens compression? if so, this isn't a factor, heres an article that explains why - fstoppers.com/originals/lens-compression-doesnt-exist-147615

[@fotoeikenburg]

Great way of simplifying and therefor clearly explaining the differences and similarities in gear usage and the final images aimed at. Every pro should know. Thanks for sharing your knowledge about the subject!

[@biscuitsalive]

Beeldproducent - film-video-foto I tip my hat to you sir!

[@mudgey2]

Very interesting! A minor point on your illustration describing depth of field, depth of field is on the image side, on the sensor side it is called the depth of focus. A bit more about the circle of confusion: A perfect lens will produce an image of a pinpoint of light as a pin point image exactly the same size. However, we don’t’ have perfect lenses, and real lenses can’t produce a precise pinpoint image, it is always slightly larger and thus a bit fussy. The size of this fuzzy image is the circle of confusion. The closer to the ideal image of the pinpoint a lens gets, the higher it’s resolving power the more expensive it is, so there is no point designing a lens who’s circle of confusion is a lot smaller than the smallest thing a sensor or piece of film can resolve. Your illustration shows the same lens being used in FF and M43, and so the circle of confusion appears bigger in the smaller sensor with smaller pixels. The best m43 lenses are designed with a smaller circle of confusion to avoid the problem you show. Regarding speed boosters, they reduce the image circle an FF lens is delivering (to cover the diagonal of the full frame, to that which is just big enough to cover the M43 sensor, so the inverse square law is responsible for increasing the amount of light per square inch on the M43 sensor. Also, the circle of confusion for that lens ins reduced at the same time. Other aberrations caused by the speedbooster may slightly reduce brightness and affect the circle of confusion.

[@biscuitsalive]

Yes, thanks, i had realised about the label on the depth of field, sorry about that, i am notorious for typos I'm afraid, and when I'm making a hasty video like this in one take, i tend to copy and paste elements to form my quick layout... then i overlooked that label... but the illustration hopefully still explains my points. :) Re the CoC, yes i could go into lots more detail there... but wanted to not let the video get to long. but hopefully it explained the point i was trying to make, then when you shrink the sensor, but don't change the lens, the CoC remains the same, but with the sensor now at higher pixel density more areas that were 'just in focus' were now becoming 'just out of focus' hence giving us a shallower DOF. Re the Same lens used on FF and M43, i wanted to get this across to show what happens, one step at a time. So what happens when we ONLY change the sensor size, then what happens when we change the sensor size AND accommodate the FOV with a native lens at appropriate FL. (and all that goes with that for equivalence.) This was intentional, but maybe it wasn't pointed out exactly why i was showing that. Re the speedbooster, i can't see where you are disagreeing or pointing out a issue there. I agree with all you say, the amount of light hitting sensor is increased when using a SB, simply because less light is 'wasted' falling around the sensor, I didn't say otherwise. I was arguing with people that say they are getting more light out of their lens by using a SB and a crop sensor, than someone who has the same lens on a FF (They think because the exposure is brighter on the crop S camera with SB, at same settings, than it is on a FF camera, then its somehow extracting more light out of the lens in total.) Note on this, eve the description/wording on the metabones website about their products, is ambiguous and a bit misleading regarding this... so i can see why some people may think along those lines. But as we both know, you can't change the amount of light going into the front of a lens, but fitting something to the back of it :D So i think we are in agreement there.

[@mudgey2]

I wasn't disagreeing at all, just trying to clarify. Good work. BTW are you from the West Country?

[@biscuitsalive]

Cool, sorry if I'm a little defensive, been fielding shouty comments for the last couple of hours on forums regarding this vid :D (den of vipers they are!) Yes, guilty, I'm Bristol born, and been living in Cornwall for last 9 years. (you can see lots of Cornish film fun on this channel)

[@mudgey2]

Thought so, used to live in Crackington Haven now in Washington DC. Visiting Falmouth Zuni in May

[@biscuitsalive]

Nice! I love Falmouth, I would have bought a home there if it had been and bit closer to my favourite beaches. I am a keen kite surfer (and instructor) in my spare time, and generally, you will often find me in the sea up to something or another. I hope you get some nice weather in May... should do.

[@ovidiulazar6226]

Great video - but a bit wrong... I have access to a tones of cameras, formats and lenses - and I have tested everything in this video. Greatly used "match" but I have done the tests. A 50mm F1.4 - will get the same amount of light no matter what the sensor size is. The ISO - is so much dependant of sensor technology that I have done the tests only on base ISO. A camera with ISO 800 full frame from 10 years ago compared to a M43 release yesterday will get worse noise level anytime. Basically that bokeh and depth of field is the FEEL - of the image. For example.. if I want to imitate the "feel" of a image shot on a FF 50 1.8 - I need a APSC 35 F1.2 - this will result the same shallow dof and in focus areas - but being a 1.2 will also expose more than the FF 1.8 - on the same settings and base ISO. A 50 1.4 is a 50 1.4 and a 50 1.4 - no matter what sensor is has behind it, the same amount of light will land on the sensor - the image due to the math that can be replicated - that is just a crop story...

[@KarmaIsABitsch]

The ISO calculation was really confusing for me in the beginning, however when I thought in stops it all made sense! Since I have to mathematically double the aperture, so from 2 to 4, in stops: 2 stops of light. I now also have to bump up the ISO by 2 stops, which is from ISO 200 to 800. At first I was like "Wait that makes no sense!" but then it all cleared up! Really nice video! Thanks a lot!

[@biscuitsalive]

Bastian Dittrich thanks dude. Yes everyone thinks differently. But glad you agree, just do it in your head with stops rather than squaring ISO numbers etc. (Hopefully others will spot your comment as it's useful for other camera heads that always think in stops of light.) The main thing to take away is that the ISO number doesn't tell you the total light creating our image. (Total photons hitting whole sensor for shutter duration) So if we can match that total light quantity across diff sized sensors, then the rest of the equation all falls into place perfectly.

[@KarmaIsABitsch]

It's actually pretty easy to understand once you get the hang of it! The basic principle has to get into your head, once that's done it's pretty easy. Yeah I'm the camera head kinda guy, calculating in stops has become second nature to me...

[@leemary7261]

I really enjoy watching this video, which teaches me a lot. However, I have a question, you said smaller sensor has shallower DOF. I want to clarify something. If I take two pictures with same lens at same focal length, same aperture and same distance to the object but one use full frame and one use APSC(1.5x) . The final image of APSC one would have a shallower DOF compared to the full frame one? that means if I scale up the full frame image 150% ( assume the resolution is not a matter), these two pictures would be different in DOF? Please correct me if I hv some misunderstand. Thank you very much

[@biscuitsalive]

Yep it’s a bit confusing. It’s technically true that if you take a FF cam and a crop sensor cam, put the same lens, at same aperture at same distance to subject. The crop sensor camera will have a shallower DOF (and will be a tighter framing). But only in the same way that if you take the FF shot, and cropped into the centre of the shot. What people forget is that DOF is not a set parameter, it’s a sliding scale. And if the image is at higher res, or enlarged then the amount of the image that is clearly sharp is lessened. This is apparent to us all, but we sometimes don’t make the connection. Eg. a shot looks sharp when viewed in the EVF. But then we get home and inspect it on a big screen and we see we missed focus. It looks sharp small. But soft when big. This is the same for cropping in (what a smaller sensor naturally does) When you crop into the centre of shot you are enlarging the image, and any “slightly out of focus” area now look MORE blurry. That’s the subjective side. Then there’s the technical side too. That’s down to the circle of confusion. The pixels are smaller on smaller sensor. (If both FF and crop sensor have same res) So the out of focus areas are MORE out of focus. The DOF will literally be shallower on the smaller sensor because the point at which the light points overlap the pixels, and blurs across 4 or more pixels is when we can detect something isn’t sharp. We can not detect any blurs tighter than something one pixel across. You have to remember there is only ONE plane technically IN focus. Even at small apertures. The rest is just slightly slightly slightly out of focus. But we can’t tell because it’s within our one pixel limit (or photosite to be accurate) If any of that is unclear. Maybe investigate “circle of confusion”

[@leemary7261]

@@biscuitsalive Thanks a lot, its a great video

[@leemary7261]

I have read many times of what you said, after that, can i say a lesser density of a senor will have a shallower DOF than a higher density sensor? Thanks

[@0afrosamurai]

Thank you so much. This video explains a lot. So what's the point of having MFT? If you need to do all that math every time, get a speed booster. I have GH3 and thinking about getting a FF Camera.

[@QuicksilverSG]

Biscuitsalive's Misconception: @18:10 - "If all other factors remain the same, a smaller sensor camera has shallower depth of field... The circle of confusion has stayed the same for that lens, but the pixel density is higher." WRONG, DOF is determined by the lens and shooting distance, not the size of the sensor. Image sharpness is likewise determined by the lens; it is not degraded by increasing the pixel density (resolution) of the sensor. The reason the cropped-sensor image appears blurrier than a full-frame image with the same FOV is simply because you are MAGNIFYING the dimensions of the smaller cropped image to match the size of the larger full-frame image. It is the SIZE of the sensor that matters, rather than the sensor's pixel resolution. We ALL know that when you MAGNIFY an image, its details will appear blurrier.

[@biscuitsalive]

Fallen Star Features the DOF of the lens does not change using a different sensor. Yes. The apparent DOF of the image does change. As I clearly demonstrate. So not sure what your on about.

[@QuicksilverSG]

"Apparent DOF"? What's that supposed to mean? DOF is a measurable optical property, not an apparition. When you MAGNIFY an image, you change its optical properties. THAT's what I'm on about.

[@biscuitsalive]

Fallen Star Features go and watch a video on the circle on confusion. I think that's where your falling down. I clearly didn't explain it well enough in my video. Please remember DOF is subjective to the medium you are recording. There is only one plane technically IN focus. Out side out that it's what's considered acceptably subjectively sharp enough or not sharp enough. and that subjectivity is dependant on the resolution you are capturing. (And to some degree the size and distance you are viewing the final image from) I generally work in 4K video. On a 4K monitor. So that's a fairly consistent way to judge the OOF/in focus areas. In which case of course there is an apparent DOF. And can be compared and judged fairly equally. If I was working in 42 mega pixel photography and it was going to be scaled up onto huge billboard posters the DOF would need to be reevaluated for that medium. The circle of confusion for this would need to be much smaller to be acceptably sharp enough. Or inversely if I only worked to 1080 HD I could get away with a wider acceptably in focus DOF simply due to the circle of confusion being allowed to spread further before the sharp areas start to look OOF. I think you need to go away and do some practical tests yourself to see what I mean. You are not considering the final image and how it's DOF is subjectively read.

[@biscuitsalive]

Fallen Star Features anyway. Sorry I don't have time right now for endless debate. About to get into the ocean. But I suggest you look at filmakerIQ video on the circle on confusion. And the role it plays on DOF. I think that's where you are falling short of understanding what I'm getting at. (He explains it better than me.)

[@QuicksilverSG]

What I'm seeing is more like a circular field of obfuscation on your part. All of the things you're trying to complicate are simply the result of MAGNIFYING a digitized image. When you do so, details that looked sharp because they were tiny become large enough for you to see how blurry they actually are. We've all seen this happen when cropping and enlarging images in Photoshop and there's nothing confusing about it. It's obvious why a large billboard needs sharper detail than an Instagram snapshot, but even there you neglected to mention that how much detail is needed depends on the viewing distance. A billboard 60 feet up in the air obviously needs less detail than one 60 inches away.

[@Thirdworld128]

Someone liked first, anyway im second to like. This is real nerdy stuff but still willing to learn and thanks for sharing!

[@biscuitsalive]

Thanks for that :)

[@herrjott9389]

thank you for your explanation, it helped a lot and i must say mft sensors are very very good, f. e. em1 II is likly even with a sony a7 iii sensor... but ... FOV + DOF + Aperture is what counts for me and i like the look of FF more. even though i have canon with less accurate sensor.

[@tangibleplanetvisualmedia1138]

One thing I'm confused about. I see by the example that it works, but if cropped sensors create blurrier images, why does the fstop need to be lower, wouldn't that make the images have more depth of field, or is it being compensated for by the wider focal length since the lens itself is physically wider and it's only the field of view your changing... I think I just answered my own question

[@biscuitsalive]

lol. U maybe did. Watch the follow up vid as there is a bit of further explanation

[@tangibleplanetvisualmedia1138]

@@biscuitsalive I did watch it, great info here thanks. Your explanation of the differing aperture diameter in relation to the amount of light entering a wider lens explains why you get more in focus at a lower f/stop on wide angle lens while maintaining the same exposure. I knew that was the case, but I didn't know why. This would also explain why halving your f/stop on a M43 sensor wouldn't create extra bokeh, but rather simply match it to the 35mm.

[@JohannesBuc]

ok, nice vid. The only problem i see with your other video, is that somebody can understand u wrong and then think they get the same DOF on a Mirco-Four Thirds with a "similar" (mathematically converted) lens. Hope you understand what I mean. But in this video it's pretty good explained, nice work. sorry for my english

[@biscuitsalive]

JohannesBuc with the other vid I was using the same lens on both. So DOF was roughly the same. (Technically it's slightly narrower DOF on the gh4 because it was slightly tighter FOV) but as explained in this vid. The DOF was the same for the lens, as same aperture, same distance and focal length was used. But just slightly diff DOF between sensors due to tighter FOV. Remember the matched equivalent example in THIS video was using two different focal lengths. That's why you need to change aperture and ISO. (Because of lens difference not because of sensor difference)

[@JohannesBuc]

But you only need a wider focal length, because of the smaller sensor size and like you said, it's harder to get more DOF with a smaller focal length. So I don't understand why you want to make full frame cameras bad?

[@biscuitsalive]

Sorry dude, but I'm not sure you quite get it. maybe watch this one again. could just be your English isn't perfect, which makes it hard to see your exact point. when you say 'harder to get more DOF with smaller focal length.' That statement is backwards. you naturally get a bigger DOF with a shorter focal length. And I'm not trying to make FF look bad, I own two of them and love them. but Im pointing out that most people get the equivalence wrong when comparing them to smaller sensors. you can get exactly the same look on a smaller sensor, if you do the equivalence correct. My points are all there in the video. Its the 'doing the maths wrong' bit i was highlighting... not that FF or crop sensors are bad, they are just different, and you have to accommodate for that difference if you want the same look on both.

[@biscuitsalive]

And to continue.. if i was attacking anything it was that manufactures are not enough fast lenses for crop sensor cameras. because they know the buying public don't do the equivalence on BOTH focal length AND aperture. (they just see something like '25mm f2.0' written on the side of the lens, and think that will work the same as '50mm f2.0' on FF...... and i will not... it will work the same as a 50mm f4) ---- Please note though, the speedbooster argument is very different than this. as that is using a the same FF lens on a crop sensor body.

[@JohannesBuc]

yes, but with a speedbooster you imitate a FF I mean you bend all the light into the smaller sensor. So I think your video "Can you spot the camera SENSOR SIZE from the shot? Full frame vs M4/3" is not a fair comparison. Depth of field means blur you get in the depth or is it the other way around?

[@something7902]

Very nice! A lot of work you have done respect!

[@biscuitsalive]

Some Thing thanks! I got fed up with arguing with people in camera groups about this stuff so thought I would try to clearly explain everything here.

[@something7902]

biscuitsalive Thank you for that! You know what still some people dont believe but at the same time they dont give any evidence just noice. I think you know what kind of childish behavior I mean.

[@ColgateFalcon56]

Brilliant video very well explained and easy to understand and grasp

[@zhanjim6374]

Hi, I am so glad to learn more things from this video. I do want to know why m4/3 or apsc camera don't have even lower ISO ? if they have even lower ISO, it will have much cleaner and longer exposure .

[@richardbutler8532]

The key detail is that ISO is part of an exposure system based on light per unit area. The underlying sensor performance, per sq mm, is very similar across modern sensors. For example, the Fujifilm X-T4, Sony a7R IV, Fujifilm, GFX 100 are essentially different sizes of the same sensor. As such, other than small differences in color filter density, they'll all clip at around the same point (or require similar exposure, depending on how you look at it). Consequently they'll all have similar base ISOs. Or, at least, the base ISO won't scale with sensor size.

[@Universal_Craftsman]

It gets more obvious, when we consider an even smaller sensor, like the 1/28" sensor of an iPhone 15 pro. The main camera is a 24 mm FF equivalent f1.8 lens, there is the first problem: manufacturers call out the equivalent focal length but not the equivalent aperture. With a crop factor of about 3.5 the iPhone has a 7 mm f1.8 which is equivalent to a 24 mm f6.3. When we set a full frame camera with a 24 mm lens to f6.3 we get the same field of view and the same depth of field as the iPhone. We also have to adjust for exposure: if we have ISO 1600 on the iPhone, we would need ISO 19600 on the FF camera given the same shutter speed. There we see that the best we can do with the iPhone is a shot at f6.3 and ISO 19600 on full frame, but with the FF camera we can open the aperture depending which lens we have to 1.6 for example which would give us 4 stops extra for exposure, we now could either increase the shutter speed by 4 stops, or lower the ISO 4 stops, which will give us ISO 1225, or divide the 4 stops differently. We can't do that with the iPhone, because we would need a 7 mm f0.45 to archive the same with our FF camera at f1.6, f0.5 is the physical limit for any lens, so this lens would be impossible to manufacture, the practical limit is more like f0.7. In conclusion crop sensors appear to have bad light capabilities, but the truth is that the smaller sensor would require lenses that are unobtainable, to get around that the only thing we can do is to increase the focal length, and if we do that we also need to increase the sensor size accordingly. If you want to get the same shot (same depth of field, same field of view) sensor size doesn't matter so much but if you want any shot (aperture wide open, maximum shutter speed, lowest ISO possible) the FF camera will always be better, because you can utilise the higher focal length to achieve a larger aperture and because of that better exposure settings.

[@Emilioh888]

Ok there's some things I don't get. Like why when you stop down the lens, the depth of field and depth of focus become bigger? I don't see a visual explanation in your video. How do you know by how much you need to expand the range ? Next is the focus plane. I thought the focus plane was a range where the image is in focus, a measured distance where everything is tack focus. According to your video , even if we are at f/8 for example, there is only one "sheet" that is in focus and not the whole depth of the environment ? Lastly I hear some people say that FF cameras compress the image differently than crop sensor in a visual way not in a file format compression way (jpg, tiff) if you know what I mean. Is that true ?

[@biscuitsalive]

Emilioh888 yes there are some things you haven’t got your head around. Maybe watch vid again. The depth of field is explained here. Yes focus plane is a single plane. You need to understand circle of confusion to understand why there is a field that is perceived to be in focus. And you are mixing up the optical effect of compression which is something distance does to the image. (Background looks nearer subject with longer lens) and compression of image. Eg. Jpg compression. (Completely different thing) Maybe watch the vid again and try to get head around the raytracing to understand aperture and DOF.

[@Emilioh888]

biscuitsalive I will check circle of confusion thanks. For the compression part, I stated that I am NOT talking about jpg compression but more about what they call "lens compression".

[@alexstevensen4292]

The amount of blurr you get in a picture is the result of the size of the so called 'entrance pupil' which is basically the size of the 'hole' you're looking through. Say you are photographing a landscape with the lens focussed at infinity and it's a 50mm 1.4 which gives a 35 mm opening. Any object nearby like a tree stem will have a blurr area that's precisely that 35mm wide. When you don't focus to infinity then it becomes a bit more complicated. Say you focus at 1 meter, there's a focussed cone 'coming' from the lens, it starts at a 35 mm width, at 1m it's at focus and at 10m is 35cm wide. If you were to put a very small light at say 90 cm it will appear as a small globe 3.5 mm in width. That same light at 10m will appear as a glob 35cm in size. The size of the blurr or 'bokeh' is the same as the size of the 'light cone' coming from the lens at that distance. Now offcourse if you reduce the lens opening the width of the cone get's reduced and you also reduce the width of all these effects.

[@michaelrojas2938]

QUESTION: I get really confused when you say to square the iso. If you square any number, then is not that number multiplied by itself? EX: 200 squared would mathematically be 200 x 200 ... and that equals 40,000. However, in your example towards the end of the video, instead of squaring the iso, you actually increased the iso two stops, because the micro 4/3 sensor is twice as small. I can understand that part, but what confuses me is how am I to determine what the equivalen iso should be on a Canon APS-C (1.6 cropped) sensor. Can you provide some clarification please? It would really be appreciated. Thank you.

[@biscuitsalive]

Hi so what I was getting at (timecode 23:28) is you take the crop factor. eg. X2 for FF - M43 or X1.5 for FF - A-PSC and you square that, and apply as you would for the rest (FL / Fstop) so for a example of the equation written down= Lets say we have a M43 camera, we want to match ISO equivalence for Full frame. (to get a good approximation match noise level equivalent, and complete the whole crop factor formula ) We take the M43 ISO of 200, we apply the crop factor and square it. So if you tap- '200' 'Times' (X) '2' 'X2' (the squared button) 'equals' and we get 800 (long winded way of saying we square the crop factor, not the iso number.) Or if the above was going from A-PSC to FF we would do- 200 (for our A-PSC ISO) 'times' (X) 1.5 (or, for Canon, 1.6) 'X2' (the squared button) 'equals' and we get 450 So in that case the A-PSC ISO would be at 200, and would match the FF at 450. (Give or take minor technology differences.... technically if you want to get into that the smaller sensors do slightly better than the bigger sensors if you stick rigidly to the crop factor squared) Tonys testing put it on average, over many diff sensor manufacturers, at 1 +2/3 of a stop, rather than 2 stops as I'm showing here. I think some of this is due to the fact M43 has a squarer sensor... and lenses tend to be brighter in the middle, so the squarer sensor is slightly more efficient once the total SS size is removed from the equation. but obviously we can fall down a rabbit hole of tiny variants if we wanted to. Personally from my tests comparing a Sony a7s and a Panasonic GH4 and a Canon 5d (plus some other random canons and other A-PSC Sonys) Personally I find the straight forward crop factor squared matches noise levels REALLY closely. (and of course matches exposure too.) But then the a7s is one of the best low light performers, when i use a canon as the FF on test, then the smaller sensor looks ever so slightly cleaner. but really nothing much in it at all I can see. So keep it simple and just use the squared crop I reckon.

[@biscuitsalive]

Sorry, just realised you had already answered the question for me... and WAY more succinctly! :D

[@michaelrojas2938]

I thank the both of you very much. I get it now. Much obliged!!!!