Depth of field and crop factor misconceptions. FOLLOW UP.

[@biscuitsalive]

Here is the original video. (This video will not make sense without first seeing that one.) kzbin.info/www/bejne/bImwnGyge8ihoqM

[@RealityCheckThat]

Anybody who can admit to their mistakes and correct them I trust a lot more than those who can't. Your points were still valid in the first vid. Thanks for the info.

[@biscuitsalive]

Reality Check we are all learning together. If u think you are never wrong you probably are not learning anything new. :) (We learn far more from mistakes than successes after all)

[@peepers4763]

The quality of your graphics is appreciated. The detail and amount of work you put in is above and beyond!

[@biscuitsalive]

Peepers 47 many thanks. Hopefully you saw the main video too. (This is just a follow up vid)

[@peepers4763]

Watched it and subscribed too 😉

[@zipfelchefchen6816]

12:50 in case of same total amount of light for the mft and ff sensor, the ff sensor would produce a darker image, right? Because less light it hitting per sq. mm?

[@user-ug9nn]

I am not a photographer, just came here to learn from you about how lens work. Thank you very much for the guide and clear explanation of how things work. I also take some notes, some images from your tutorial, for my future refresh of knowledge regarding this subject. When I take notes I also analyze the information trying to understand, and I also find a small misrepresentation. The depth of focus asymmetry is also away from the lens not closer to the lens.

[@jpsteiner2]

Thanks. This and your previous, related video, were excellent in putting DOF, ISO, etc in to proper perspective as it related to FF and MFT. I'm a big MFT fan, but I know it's not necessarily for all types of shooting. I think you probably need a pint as well as a tea.

[@fuzzywuzzy599]

Isn't the amount of light more concentrated and therefore greater when a vintage lens is put on a crop sensor and aperture is sufficiently open to allow it through to the sensor?

[@jeffhampton7405]

The thing that bothers me about the Angry Photographer isn't the guy himself. He's laughably easy to ignore. It's the number of people who seem to think he knows what he's talking about.

[@ElGrecoDaGeek]

His audience explains the resurgence of Flat Earth in the era of the internet. Pied pipers who speak with authority yet have none (or little) swaying the easily swayed.

[@jonathansim8725]

I can't thank you enough, I stumbled upon this video on accident and it answered questions I didn't know I even had for my aps-c sensor dslr. Thanks so much :) I really learned a lot!

[@HundredAndThree]

Thanks for these vids. I constantly have to explain to people at work these principles & you have given clear examples of how to explain things so that they can understand. Appreciated!

[@ivansmiljkovic88]

50mm at f4 vs 25mm f2 same SS and ISO...will it be the same exposure? Will 50 1.8 on fx camera give me more light than on DX camera?

[@franciscoreynosom8919]

I think all concepts were crystal clear from the begging (original video) and very well explained. Fantastic Job!

[@biscuitsalive]

Thanks! So hard not to make a couple of tiny mistakes with such a subject.

[@Lesterandsons]

When we talk about equivalence, two items matters the most, lens entrance pupil and format sensor area size The concept of "Étendue" also helps to understand total light gathering When to dof, what matters is entrance pupil and distance to the subject.

[@lakshmanprasad2798]

Thank you for very clear explanation of scientific rationale behind the most difficult concept of crop factors, circles of confusion etc. I am a newbie to photography, a beginner hobbyist. Appreciate if you could please clarify this one critical parameter related to fixed focal length lenses. If the focal length of a fixed focal length lens is 50mm with an f-stop of 2.8, then the diameter of the aperture is also fixed at 17.85mm ie 50 divided by 2.8. If these two parameters are fixed, only variable parameter left is the shutter speed. Does it mean that the camera will be able to focus on objects located at various different distances just by adjusting the shutter speed depending on the available light? As a consequence of above, do we always have to use a tripod for fixed focal length lenses, in order to over come the issues of camera shake due to low shutter speeds determined by the camera, during low light situations. Does it also mean that fixed focal lenses are in effect, constant Aperture priority mode, by default? It is a photography paradox that these fixed focal length lenses are also called as fast lenses. If the above points are correct they could act as slow lenses as well! Looking forward to seeing your response :-)

[@РоманЛеухин-й2ы]

First of all, the f-stop on lens usually represents the maximum (widest) aperture possible on this lens, but you can control aperture via ring on lens or inside your camera. Usually cameras have Aperture priority mode (you set the aperture and camera chooses the shutter speed), and Shutter priority mode (vice versa). Fixed focal length lenses (a.k.a. prime lenses) are called "fast" because they usually have wider maximum aperture compared to variable focal length lenses (a.k.a. zoom lenses), just because prime lens have simplier construction and have more free space inside to create wider maximum aperture. So they capture more light and allow using faster shutter speeds, and get rid of using tripod. Hence "fast" :)

[@trackready8026]

Hey, just wanted to let you know I appreciate you taking the time to make these videos. Your diagrams were simple, but I feel they were adequate for the explanation. I'll definitely send this video to some people as your explanation is certainly better calculated than when I try to explain similar principles. It's interesting that as small sensor camera's are getting more adopted by working professionals certain facts slowly are getting accepted in the community. The last one that I feel is completely misunderstood is compression. It seems people now can except focal length equivalence (that wasn't too bad), a huge step was people accepting aperture equivalence (took way too long), ISO equivalence is getting there, but it seems people can not accept that 'compression' is not determined by the focal length alone, and that a equivalent focal length and aperture will have the same compression.

[@richardbeck4193]

I’m interested in the case where the M4/3 is set to f4 instead of f2 would the increase in DoF be 2x ?

[@okaro6595]

No, it would reduce the circle of confusion by half. It can increase depth of field by a different amount. For example it can cause the depth of field to reach to infinity which is infinity times more.

[@cengavis8292]

Hi! Just came across these two fantastic videos which I found very well made and precise. Thank you! I have one question for you that I think might be interesting to analyse considering focal length, DoP, f-number... for two cameras with two different sensor sizes. Consider Cam1 a FF with ISO 800, 50mm focal distance, 5 meters to the subject, f2.8. Then consider CAM2 a MFT camera (crop factor x2). Imagine that you want to have the exact same image in both cameras. What is happening if, instead of going with a 25mm lens, f2.0 aperture, ISO 200... you simply move yourself away the double of distance from the subject - in this case, 10m (crop factor x distance). Can you please elaborate this in terms of FoV, DoP, noise, ISO, f number, and bouquet? I know that in many situations it is not practical to double the distance to the subject but there are others where it is quite possible. Your comments are greatly appreciated! Thanks!

[@noplastik]

50mm / f2 has a 25mm input lens diameter, not a diaphragm diameter. It's simple: 100mm / f2.5 has an input lens diameter of 100: 2.5 = 40mm, 200/4 = 50mm. This is the theoretical f, the practical value is T, which calculates the loss of light. DOF will be the same for all lenses when shooting from the same distance. Only the angle of view varies depending on the focal length.

[@ArberBaqaj]

Loved this one as well! You should make one about the speedbooster also.

[@TomFoolery9001]

Yeah I would like a little more math on the speedbooster and how to figure that into the calculations. When they say it adds a stop of light is that an additional stop or just the stop that the normal math is taking into account?

[@richardbutler8532]

@@TomFoolery9001 Speed boosters are sometimes also known as 'focal length reducers,' (They're the opposite of teleconverters, basically). So if you mount a 0.71x Speedbooster on the back of a FF 50mm F1.4 lens, the combination ends up with a focal length of 35.5mm. However, the aperture diameter hasn't changed (it's still 35.7mm). A 35.7mm aperture in a 35.5mm lens would be F1.0. The key thing to note is that you can only speedboost lenses designed for a bigger format (you need a wider image circle to condense down to your smaller sensor - that's where the apparent extra stop is coming from). Now, work out the behaviour of a 35.5mm F1.0 on an APS-C sensor. It's a 53mm F1.5 equivalent. Sound familiar? Essentially what a speedbooster does is condense the full field of view of the lens down from, say FF to APS-C, shorten the focal length, which boosts the F-number, and the net effect is that you get behaviour much more like that of the original lens on its native format. That's why FF->APS-C boosters are usually around 0.71x reducers: because it approximately cancels the crop factor of APS-C. The only downside is that a 35.5mm F1.0 lens is more likely to see you hit your max shutter speed than it would as a 50mm F1.4 on full frame (assuming similar base ISOs).

[@Sanemancured]

Anyone who is so totally confident of his own knowledge and scathing of others as Ken is sadly doomed to eventually fail. The wise are open to getting things wrong and go back to basics to rethink. Great work. This engineer likes the approach.

[@ElGrecoDaGeek]

Sadly, in this day and age I'm not so sure. There are enough nutters to support him and his little corner of YT as the last 6+ years have shown given his channels growth since he went 100% off the rails on this metaphysics mumbo jumbo word salad monologues (check it out if you dare).

[@Sanemancured]

@@ElGrecoDaGeekI daren’t. I just don’t need the negativity.

[@Be-Es---___]

But how about full frame lenses on crop sensor camera's? What I do want to see is how full frame lenses act on crop sensors. E.g. Will I see the difference between f1.4 and f1.8 on my crop sensor? Or will it be outside my crop sensor view. Or does the f1.4 act as f2.1 (f1.4 x 1.5) and the f1.7 as f2.5 (f1.7 x 1.5)?

[@biscuitsalive]

FF on crop will simply be the same image but cropped in to centre. so the DOF will be the same as if you simply cropped a FF image. technically the apparent DOF will be shallower due to what happens to the circle of confusion. but remember your framing will be tighter, so you will need to step back from model to get same framing, which in turn makes DOF wider (due to distance from model.)

[@nicksouthorn1248]

Very good but the MFT sensor is a little bigger than a quarter of a full frame sensor so the ISO crop factor squared is an approximation. ISO can be set in subdivisions of stops so it could be closer.

[@biscuitsalive]

If you are talking 16:9 for video (I mainly shoot video) Then it’s pretty much 1/4 of a FF. (M43 is squarer than FF sensor. But the extra height is wasted for C4k or 16:9)

[@nicksouthorn1248]

biscuitsalive no I'm talking about your diagram with four M43 sensors inside a FF sensor. They would not fit because the M43 sensor is 28.125% of a FF sensor, not a quarter. Your diagram is not to scale. The crop factor squared rule is an easy approximation to use but is not an accurate calculation as you claim. FF ISO of 200 works out as M43 equivalent ISO 710. 200*(1/0.28125)=710. Not practical to use while shooting so the crop factor squared estimation should be used as it is quick, easy and goes to a full ISO Stop, so you were right to mention it. However you asked us to identify any inaccuracies in your explanation and your diagram is not accurate. The crop factor squared rule is a simplified approximation. Hope this helps. Overall your explanation was very good and I'm sure it will help many people.

[@okaro6595]

Because the sensor shape is different it cannot produce same image without additional cropping. If you crop to 3:2 it increases the crop factor by 4%. If you were to crop 3:2 to 4:3 it would increase its crop factor by 8%.

[@VynZography]

Hi. I just linked the original video and this one in my latest upload because you explained it so well. Thanks!

[@TomFoolery9001]

So for figuring in a speedbooster of .64 for say a 200mm f4 lens on a micro four thirds body. Would the math be 200 * 2 * .64 for a resulting 512mm f/7.1 lense? I'm just trying to make sure I'm doing the math right with the speedbooster in the mix. Thanks for the great breakdown!

[@farqend]

speed booster .64 = 128mm @ F2.56

[@okaro6595]

No, the lens will be 128 mm. Do not confuse the equivalences with actual changes in the lens. The speedbooster really changes the lens.

[@denisc.1282]

He probably meant that angle of view doesn’t effect the amount of light getting to the sensor

[@ecsays]

A contentious issue indeed. I follow all of the math and logic and results you have outlined and given an engineering background, I fully understand them. There is however one small thing that nags at me. For over 40 years I have been using the same handheld light meters to determine correct exposure with film cameras across various camera sizes (either incident or reflected measurements). And what you haven't explained is why either my large format negative (5x4) which receives a lot more light than my 35mm negative (according to your line of thinking) or the 35mm negative should be incorrectly exposed if I used the same light meter. Remember that light meters did not account for negative size nor did they account for focal length or crop factor etc.. You will say that ISO is measured as light falling on a square inch, so what about film ISO? If it is the same, then light meters should have had a way to compensate for that or there should have been dire warnings in the manuals about this and the jump from 35mm to medium format is similar to m43 jump to FF however, the jump from 35mm to 5x4 or 10x8 negative is so huge that the exposures would have been totally off on one or the other based on light meter readings. Yet they were not. How do you account for that?

[@biscuitsalive]

hi, yes exposure is measured differently. i think this is one of the sticking points for many on this. I'm am currently working on a video that shows much more practical results/comparisons regarding the ISO equivalence. But to briefly explain, the ISO is measuring the GAIN added to boost signal from sensor. (just like any amplification for audio etc) and a smaller sensor at the same ISO number is getting the SAME exposure. BUT across the whole surface of the sensor, there is less total photons hitting it, simply because of its smaller area. so essentially the ISO is applying MORE relative gain to amplify the signal to create the whole image. even though, if measuring a square inch of that sensor the gain would be the same. (its technically adding the same gain, but because the sensor is smaller the original signal is a lot weaker anyway... hence 'relative') i hope this makes sense.... and this would be exactly the same for film. if you take it to imaginary extremes it may help you see what i mean. so if you had a piece of film 1 meter square, (lets say at ASA 100) the exposure would be the same for a pice of film 10 cm across. at ASA 100... but the huge pice of film would have (in total) a massive amount of light hitting it compared to the small piece, ... and its ALL the light that in TOTAL makes up our WHOLE image is what is important, not a arbitrary portion of that image. (with the portions size only dictated by sensor/film size)... so yes. exposure is one thing. but it doesn't tell you the total amount of photons that go into creating the entire recorded image. if you are comparing different sized sensors or film stock, and you want to match image noise, you need to level the playing field and allow both images to be made of the same total amount of light fall. (same amount of photons) and this will mean making the smaller footprint brighter, as it is simply concentrating the same light over a smaller area.

[@4CardsMan]

The exposure is the same for all film formats, but the smaller negative requires more enlargement to match the field of view. So, if you are shooting HP5 in 4x5 with a 150mm lens at f/11, and you expose at box speed, then to get the equivalent granularity (noise level) and field of view and depth of field, you would need to shoot FP4 in medium format with a 80mm lens at f/5.6 or Pan F in 35mm with a 50mm lens at about f/3.5. If you shoot FP4 in all three formats, you have to open the aperture as you go smaller to get the same depth of field, but you can only get the same noise level if you print smaller. To get the same noise level, you would have to print 4x5 at 16x20, 6x6 at roughly 11x11 and 35mm at roughly 5x7. The light meter works for all formats because of how f/ numbers and ISO are calculated. But equivalent exposure does not mean equivalent field of view nor equivalent noise level.

[@howardmaryon-davis666]

All these comments are good. I wonder if a theoretical analogy could be made not only about sensor size compared to film, but also light receptor density on the sensor equating to fine or coarse grain film in terms of iso speed and noise? Just a playful thought. Lens manufacturers should stress angle of view, not focal length when declaring 35mm equivalents.

[@ecollazo67]

Total light on sensor has no meaning in photography. Pixel pitch is what matter to exposure. The author of this video is wrong. www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

[@aes53]

Finally, somebody understand this. It's photon flux per unit area of the sensor surface. While a full frame sensor accumulates more TOTAL light than a crop sensor the intensity per unit area is the same on both, which is why the exposure is the same when you use an external light meter for both 35 mm and 6x6 film sizes.

[@kchong228]

Excellent. U clarify the misconception. Many thanks.

[@l00kmore]

Correct. Similar discussions have creeped on other places. Most people interpret the ISO as a unit of image noise (which it isn't) and aperture as a unit of depth of field (which again, it is not). Likewise, the old 35mm film guys like myself tend to interpret focal length as a unit to measure the field of view (which it could only be if every camera had the same sensor size)

[@davidhollingworth9392]

Great video(s), very informative. P.s. Sorry for commenting on a 2 year old video but I do have a couple of follow up questions, Q1) is a lens that is designed for “full frame” e.g. a 70-200mm f2.8, technically a 105-300 f4.2 when used with an APS-C sensor (with a 1.5 crop). And Q2) are lenses that are made specifically for APS-C sensors any different when it comes to the f(n) they are marketed as? (I.e. I know the focal length is still affected by crop factor but what about aperture?). Thanks

[@okaro6595]

All lenses are marked with their actual focal length and speed. They cannot ever become anything else (not counting teleconverters and speed boosters). The fact that smaller sensor produces different results is entirely result of it being smaller.

[@aFLYER1980]

Quick question, i get most of what your saying about crop factor, and a f2.8 lens on a m3/4 has the same DOF as f5.6, but does a f2.8 lens on m3/4 let in f2.8 amount of light ( ignoring t-stops for now ). You may have covered this and i simply missed it.

[@biscuitsalive]

aFLYER1980 did u watch the original video for this. (This vid is just a follow up) that explains much more. But in answer. M43 native 25mm f2.8 Full frame 50mm f2.8 = The exposure on both is the same. But the whole image on the full frame is constructed from 4 times the amount of photons. The 2.8 aperture on the FF cam is physically twice as wide as the 2.8 on the m43 because of the focal length. Twice the width = four times the area. So the answer isn’t as straight foreword as most people think. They simply think if brightness / exposure is the same. Then that means same amount of light. And yes if you looked at a square millimetre of both sensors, they would both be getting the same amount of light. But that full frame sensor has 4 times the area. So it’s making its image from 4 times the total light.

[@okaro6595]

The intensity of the light is same as with f/2.8 on FF but the total amount of light is same as with f/5.6.

[@joaomarques7180]

amazing videos thank you so much, you cleared up all my doubts

[@danncorbit3623]

Theoria apophasis Probably thought you meant focal distance when you said wide. For instance a 14mm lens is a wide lens. I didn't read his response, just a guess. A lens that is wide physically obviously lets in more light than a lens that is physically narrow.

[@ElGrecoDaGeek]

Focal length/distance and the characteristic "wide" are directly related so this assumption on Ken's part is very unlikely. It is more likely Ken is out of his element. Focal length is used to determine how to categorize a lens as either being a wide or narrow (telephoto) FoV lens. They are synonymous.

[@lentsi6595]

God, i"m now crystal clear and better off than most of them. How I wish I knew this channel earlier.

[@Quetzalcoatl0]

Ok so i watch the original and the follow up video. I agree with everything but i don't get one thing. Where you explain about how higher pixel density changes the depth of field, in theory is true and i 100% agree with it but in practise if you compare a 20mp ff and a 50mp ff, even thou the pixel density is massively different, the bokeh/depth of field should look exactly the same, because the pixels are soo small that you should not be able to physically see the difference. I might be wrong, but no one is talking about how he changed from a 20mp FF to a 50mp FF and saying that he had difference in the depth of field. I can't even find a video/blog/forum with real world examples. I really wanna see 200% or even 400% zooms on photos taken with close to the above mentioned megapixels.

[@biscuitsalive]

Quetzalcoalt hi. I think the bit you want to look up is the circle of confusion. Filmmaker IQ did a great video covering this. (They go into more detail than I did) It shows that if you raise the pixel density the acceptable depth of field narrows. (Depending on how you judge the final image of course. Viewed across a room on a TV it would look the same. But on closer examination you would notice the OOF areas. ) This is all true. And it’s why nailing focus for 4K work is much more critical than nailing focus for FHD. But also bare in mind if you keep the total resolution the same. (So both 4K ) And you shrink one sensor. This is raising the pixel density. This is why technically speaking a smaller sensor has a narrower DOF than a large sensor. (Against popular belief, but technically true) But of course the smaller sensor has the narrower FOV for the same focal length. So then you have the framing different. So it’s all a juggle between all those factors if you want to match shots between very different cameras.. Or you simply want to fully understand what’s happening inside your camera. I hope that helps.

[@gauranggppatkar2968]

It feels very good when somebody accepts their mistakes only to give us correct knowledge. Great explanation anyway.

[@EnterAName-l3y]

10:40 Nice video, however, I think it would be better to mention that all this math works if both FF and m43 sensors have the same number of pixels on them, in case, say, 16 mp on m43 and 64 mp on FF each pixel would get the same amount of light for the same F value.

[@okaro6595]

Pixel count is not relevant to this. Nobody cares about the amount of a light to an individual pixel. The myth that low resolution is good for low light has been debunked.

[@stevestrasser6833]

Really good explanation! Thanks for that. Unfortunately, I can't find the article about "background compression" on lensrentals.com. In fact, there are no articles at all. So I checked out the blog on www.lensrentals.com/blog/: nothing. Then the geek articles on wordpress.lensrentals.com/blog/category/geek-articles/ : still nothing...

[@CzornyLisek]

In complicated(multi element) lenses "compression", more correctly called "perspective distortion", is not so much tied to focal length. Also it's possible to create lens that(almost) do not have any "perspective distortion" thus is telecentric. cfile2.uf.tistory.com/image/2666284655C162E10DEF8B Another thing is that many lenses have "mechanical vignetting"(do not confuse with "light falloff" that also happen in lenses). It create kinda a aperture that work stronger the more on side light rays are(Because of that, apparently it made designing lens easier -> cheaper overall. And it's reason why so many cheap or/and old lenses have "cat eyes"). Also it's not true that it doesn't matter where aperture is, even when it's just single lens. c1.staticflickr.com/3/2895/33820191350_e3f4a31bab_o.png c1.staticflickr.com/3/2947/33361879804_a22dd3f025_o.png c1.staticflickr.com/3/2818/34163434476_062faa430f_o.png In this example it's clear. Everything change but generally -> When aperture is at the back it create a hell of front physical vignetting. Front aperture seem to creating huge coma. While in middle it's perfectly usable lens. For single lens lens c1.staticflickr.com/5/4165/34073982691_341a92da5a_o.png c1.staticflickr.com/5/4194/34073982641_2786a99df1_o.png c1.staticflickr.com/3/2817/34073982841_3f7ec2e2d3_o.png

[@ricban1950]

All lenses, NO MATTER WHAT THE FOCAL LENGTH IS have the SAME DEPTH OF FIELD when FOCUSED on the SAME DISTANCE using the SAME APERTURE. A 50 mm lens remains a 50 mm lens whatever the sensor size is. The IMPRESSION of DIFFERENT DEPTHS OF FIELD is an ILLUSION CAUSED BY DIFFERENT ANGLE OF VIEW. A 50 mm lens will be WIDE ANGLE ON A 6 cm x 6 cm sensor, STANDARD ON A 35 mm SENSOR and a TELEPHOTO on a 4/3rds SENSOR. It remains a 50 mm lens whatever the sensor size. This can easily be demonstrated by photographing an object with different focal lengths and ENLARGING the object to the same size on a screen or in a print. The AMOUNT of BLUR WILL BE IDENTICAL. The apparent increase in depth of field when wide angle is because the objects are smaller so appear sharper because the blur is smaller. Conversely for telephoto where the blur is magnified giving an impression of shallower depth of field. I knew this more than 50 years ago when I couldn't afford a telephoto lens and zoomed in using a good old fashioned enlarger.

[@okaro6595]

No, focal length has a significant effect on the depth of field. However, if you change the distance so that the subject is same size then the depth of field is roughly the same.

[@ricban1950]

Take a photos of a beer bottle at the same distance with the same aperture using different focal lengths. Then print each photo such that the bottle fills the size of the paper. You will then notice that the amount of blur behind and in front of the bottle is the same in each print. I am correct.@@okaro6595

[@something7902]

Again very very good work! Don't mind those rude people they don't have nothing real to show us. Only opinions which don't matter. 📸

[@biscuitsalive]

Some Thing :)

[@stacymuller585]

Great couple of videos (and maybe the best diagrams I've seen for describing DoF), but I understand that the larger aperture (or more accurately the larger entrance pupil which is the aperture as magnified by the front element) of the 50mm lens over the 25mm lens is to compensate for what is a greater light fall-off with a longer focal length (with lens elements moving further from the sensor) - not unlike a projector brought further from the screen it's projecting its image on, creating both a more magnified image and a darker image. I suspect that this is more the issue at hand than requiring a smaller entrance pupil or aperture to compensate for a larger field or "wall" potentially creating more total light to enter the lens. While a larger sensor has more potential to gather more (total) light than a smaller one (especially if assuming similar photosites with similar fill factors on both sensors), I doubt that there is concern in the lens design for the larger wall or even if we can say that the larger wall means more total light. In fact, there can be an OPPOSITE effect with the greater focal length... Let's say we are photographing a human face in a scene where everything else is in total darkness. More of the (perhaps spot-lit) face fills the frame with the longer focal length lens than the shorter focal length lens given the same subject distance - more overall light then albeit at the same f/2.0 exposure. But I'm thinking that that should not be a concern either. If not for the larger aperture size and the power of the front element to magnify the aperture to the proper entrance pupil size, we would have a higher f-stop than f/2.0 and an underexposed face - for EITHER lens, but worse underexposure and the highest f-stop for the longer focal length lens ... as I understand it. So does the angle or field of view (based on both the focal length and the sensor size) or even just the angle of coverage of the lens or its focal length or its magnification if you will have any sway on how much light the lens gathers or its exposure? As much as I love what seems to be your theory, at least, of the larger wall/field (and wish a certain someone else to be wrong), I suspect that it is not right based on what I said above. Perhaps you are still effectively right though if you meant that the angle or field of view affects how much light at least POTENTIALLY transmits through the lens with the less of that with the greater focal length - just maybe not in the way you thought. Take into account for instance that the aperture hole size does not change when adjusting the focal length of a zoom lens (regardless of whether it is a so-called variable or constant aperture zoom lens - "aperture" referring in this case to the f-stop), but the size of the entrance pupil, thanks to the front element working as a magnifying glass basically, usually DOES change and MUST lest we would have higher f-stops (or no ability to truly have a constant aperture lens without actually having to change the aperture hole size throughout the zoom). Variable aperture zoom lenses of course tend to have higher f-stops at their longest focal lengths (which again would be higher without the front element). And for a constant aperture zoom lens, without the front element (working to magnify the aperture hole ever more with ever greater a focal length), we could not allow the TRUE aperture hole size to stay constant, and would not be able to achieve the very low f-stops that we can.

[@hav6301]

"one 50mm on a FF and another 50mm from different manufacturer on the same camera is gonna have the same field of view" theoretically yes but if you try it it's never the case. Even same manufacturer lenses, p.e. I compared Canon EF 50mm f1.8 and f1.4 and weren't equal. Then compared to 50mm Sigma and got yet a third field of view.

[@biscuitsalive]

Hugo AV always going to be small variables. Not worth worrying about really. As long as you have your head around the basics you can make all the adjustments u need. (From my experience the FOV differences are very minimal. Even when comparing diff system lenses. Eg my 12mm m43 lens closely matches my 24mm full frame lens. )

[@PhilUKNet]

As a KZbin content creator you very quickly become aware of how many angry people there are out there. It can be quite disturbing. You make what you think is a harmless video that will offend no one and some people erupt into the most outrageous hissy fits. They really need to watch their blood pressure. No one is forced to watch videos. If you don't like something, stop watching it and watch something else. Shame I didn't discover your videos sooner, but they have only just appeared in my feed. Thanks again.

[@flexable9256]

Hi, I just discovered this channel. I like these explanations and format - better looking at drawing explaining the concepts than looking at someone speaking. I followed both videos and totally agree with the maths and physics, but there's one aspect that bothers me still : photosite. When you explain the total amount of light difference between two sensor size, I don't really see the point. What matters here is your photosite size, which will be related to the pixel density. Sure a smaller sensor is more likely to have an higher pixel density... but that's not a given, especially those days when manufacturers are back with the MPixels war. I believe this is a bias in your test: you do not take into account the pixel density. Two different sensor size with a similar photosite size receive the same amount of photons per photosite, and thus have the same noise level, assuming they are of the same technology (say both are BSI from the same manufacturer and same generation). I really can't see why the total amount of light is important. That's my understanding of a CMOS (or CCD) sensor: every single photosite collects its own amount of light to transform that into electrons, and it doesn't matter for that photosite that there are 40 millions of them or not, it doesn't change its reading. When I do nightscape photography, milky way shots for example, that pixel density is critical: not only for the signal quality (more light can be gathered so less noise), but also for star trailing effect. Bigger photosites allow me for longer exposure time without that trailing effect (and so more light, less noise too). You should take that into account in your real life examples. I'm wondering if omitting that is not driving you to incorrect conclusions. It's a very difficult task to try to do real-life examples of different camera using different technologies.

[@sonvfave]

It would be a good test to use a ff 50 at f4 and then shoot again with mft at f2.. just saying Love your work!!

[@biscuitsalive]

Matthew White hey. Did you not see the previous video. This was just a follow up to that. Real world tests in there. :)

[@robbyboyo]

Very sophisticated diagrams.

[@biscuitsalive]

robbyboyo lol. Very basic diagrams. :) Tried to go for clarity over style here.

[@howardmaryon-davis666]

Insignificant error, the concept is still correct. Now try explaining the Scheimpflug relationship in a large format camera! I have subscribed. The American/Greek fellow is a ridiculous buffoon who spreads misinformation, he clearly makes things up to suit his point of view.

[@biscuitsalive]

Howard Maryon-Davis thanks. But u can see why I wanted to clarify my small errors. Yes that angry photographer is controversial simply to get views. He is a caricature. And I doubt he even believes half of what he says. He just goes for maximum drama every time .

[@lowcostfilmmaking264]

guy you forget to match aperture in your shot examples, or it is full of writing errors

[@biscuitsalive]

Low Cost Film Making do you want to point out one specific example?

[@jjampong]

Both camps are correct. It just depends on which side you're on. Russians believe russian media, Americans believe american media. If you're a full frame user, if you want to replicate what the aps-c has taken using the very same lens, you simply crop the picture and it would have the same depth of field. ON THE OTHER HAND, If you're an aps-c user and you want to replicate what full frame (say 50mm 1.8) has captured, you cannot simply crop, you need to use a lens with a wider field of view, and that would be 35mm to account for the crop factor. And since it's a no brainer that 50/1.8 would have different bokeh to 35/1.8, you have have to use the crop factor and use 35/1.2 to get the same bokeh.

[@sj257257]

All makes a lot of sense to me. Thanks. Now get on the bike and go enjoy the weather (I explored some of Gwithian last weekend #legkiller)

[@biscuitsalive]

Simon Jones Gorgeous day out there today for it. Been distracted with life stuff today though. :( (Cat funeral this morning.) Wilf will be very missed.

[@sj257257]

I did a lunch time dash around Goss Moor. Bummer to have life get in the way. Did you get to Watergate at the weekend for Legends of The Bay? I managed some still Saturday afternoon. Could be good at Pentewan tomorrow.

[@biscuitsalive]

Simon Jones nope didn't make it. Need to get out in the world before I miss more of what's going on.

[@sj257257]

Not to blow sunshine up your backside, but you capture some great stuff. So get out there and get capturing.

[@biscuitsalive]

Simon Jones getting my niece down soon. She's a competing down hill mtb girl. Going to do some stuff mixing live action with animation. Should be a cut above the average hopefully. :)

[@sonvfave]

haha so I told you to do some thing u already did.. hopnesty had forgotten! thats my story and Im sticking to it!! so, It begs the question of rating lenses, maybe we should have light per cubic cm?

[@biscuitsalive]

I think in an ideal world we would forgot the old systems and go with Tstops/transmission stops (instead of Fstop) and a FOV angle (probably horizontal, followed by vertical) that would be way more useful to someone buying a new lens. and none gets confused when they swap to a different system.

[@sonvfave]

but that would require two very challenging things CHANGE and Commen sense

[@CzornyLisek]

Name of lens(for example 50mm F1,8 IS ASPH) is not technical specification. That's is very important in first place. Also T stops won't rly work in photography as build in apodization filter is a thing. Also one manufacturer F1,8 is T1,9 another F1,8 is T2.1. And generally people more care about bokeh and focus than how much light sensor get.

[@TheViscountOmega]

You should do a whole video on lens compression within different formats--full-frame, aps-c, medium, 4/3rds, etc.. . You be a massive legend, up there with George Eastman and the Lumière Bros. People would speak reverently of you for centuries to come.

[@biscuitsalive]

TheViscountOmega :D Il think on that! :) Been messing with medium format recently. But I'm not sure compression really changes that much once you have matched FOV and distance to subject. So when you do the CF maths and make adjustments as I explained in the last vid, Then compression should match too. But I haven't really gone into practically checking this is true yet. So I am curious myself. Prob best to do some practical tests between medium and m34 If I can match those extremes the rest should be easy peasy. :)

[@ds-09xz]

amazing! Thank you!

[@biscuitsalive]

No, thank you. :) (I hope I made things a little clearer, and not just muddied the water.)

[@mahfeww]

Theoria apophasis is a good guy at heart. Thanks to him, you made this video. He does want the best for everyone. I wish people would treat the guy better. He might be angry all of the time but he does have good content and is very helpful. Just don't think of it as him attacking you, it's his way of helping.

[@biscuitsalive]

I don’t think you would feel that way if you saw the personal attacks he dished out. Direct messages etc. Proper loony. I hadn’t even heard of him and he was sending me some weird stuff.

[@mahfeww]

@@biscuitsaliveDon't take offense to it. We need all of us to learn and grow. Everyone is different

[@Sanemancured]

@@mahfeww You’re making excuses for his flawed personality

[@mahfeww]

@@Sanemancured I like anyone who seeks the truth. The truth wants to be found. It is always important to question. I am one of the few ready to take a lashing from this guy and think of it in a positive, questioning and learning way. Society has trained people to just hate anyone with different views. Flat earth is real but you'll probably think I'm a loon

[@Sanemancured]

@@mahfeww Matthew, I do have an open mind, at least more open than many. I am English. Ken’s brash ‘everyone is an idiot but me’ grates on my cultural English sense of right and wrong. Yes he is intelligent but he is also ill in my opinion. The obsessional things he gets up to ‘behind the scenes’ to vilify and besmirch others points to this. I’ve no personal beef with the man but I see great flaws in his ego fed beliefs. Yes everyone is different. But some are more enlightened than others whatever their level of intellect.

[@D4ni3lS4nk3]

Please do not say "apply" crop factor, is less cofusing say "multiply", by the way both videos are great, keep with the good work

[@biscuitsalive]

Daniel Castillo fair comment. It’s kind of just how I think of it. You apply a crop factor equation to the numbers to get an idea of how final will compare to full frame. But I get what you are saying. :)

[@D4ni3lS4nk3]

biscuitsalive that is what I thought, but for those that dont know much (or nothing) about this, may not know is they have to divide, sum or multiply. But again, is a really good video

[@biscuitsalive]

Daniel Castillo agreed. And thanks.

[@CurtisZondag]

Great video.

[@tomyanowitz-cinematography7142]

Thanks for this video :)! This CineTomy channel is a youtube channel I just created that is quite similar to yours, if you have some time to check it out that'd be great ! In my first videos I take an in depth look at dynamic range, and go over things most people aren't familiar with I think.

[@biscuitsalive]

il have a look, thanks

[@tomyanowitz-cinematography7142]

Btw we had a somewhat long back and forth in the comments of your previous video but I was on an other account

[@biscuitsalive]

Ahh ok, thanks, makes a bit more sense now :)

[@VR_Wizard]

Every second of you video matters raging about a commenter is not helpful. It makes you appear thin skinned and distractes from the actual content.

[@skakdosmer]

You're using about fifty times too many words in this video (unlike in the first video). If you want people like Ken Wheeler to understand this, you should make it much simpler! And as it basically very simple stuff, it can be said in very simple ways. Also I think you should have waited untill your “clouds of irritational dust” had settled, before making this video. You may be right about the man (I don't know), but I think you should leave the rude remarks to him. That's the one thing he does better than you. Don't get into a fight, 'cause you can't win.

[@ElGrecoDaGeek]

Fighting Ken is pointless. He only wins in his mind and never loses. But engaging him is still worthwhile endeavor because reality doesn't care about what Ken Wheeler thinks.