Depth of Field Myths: Does Focal Length & Sensor Size Affect DoF?

[@geraldundone]

Thanks for watching! 😃 I hope my explanations were clear and helpful. There was a section that I completely cut from the video because I felt it bogged down the flow and made it much more confusing, but if you’re interested in knowing more about how focal length affects depth of field, read below. In the video I suggest that focal length has no direct affect on depth of field--only secondary, and this is only true if the goal is to maintain a consistent size of the subject in the frame or magnification. If we remove distance to the subject as a condition, then focal length becomes a direct influencer on depth of field. This often seems confusing, because you’d think a longer lens with a greater focal length would have a deeper depth of field because it has a more narrow field of view, but what’s actually happening is the longer lenses are increasing the noticeability of discrepancies in focus. Basically, if rays aren’t meeting perfectly at the correct plane, they cross over each other and can go on infinitely getting further and further apart. So longer lenses allow these less-than-perfect alignments to get further from each and thus further from focus when travelling down the longer focal length. Where a wider lens, which converges more powerfully, cuts the errors off sooner so they’re less blurry when compared to the point of true focus. More simply, longer focal length lenses magnify or bring things closer to you visually, which includes exaggerating discrepancies in focus, making the range of acceptable focus more shallow than if you used a wider lens. As explained in the video, however, this is easily overcome by achieving the same subject magnification or filling the frame equally with the subject when using a wider lens. So, as you can see, it’s both true and untrue that focal length affects depth of field, depending on what you’ve determined to be the primary goal. If your goal is to have equal subject weight, focal length will have no important affect, just move the physical location of the camera or the subject. If, however, you wish you maintain a constant physical distance, then focal length will be a primary and direct factor in influencing your depth of field. I hope this addendum didn’t obfuscate the utility of the video too much. And to those who braved the further reading, I hope you have a wonderful day! 😃🙏💗

[@josecolon8143]

Gerald Undone you are a natural educator! Bravissimo!!! 🎉🎊🌟🍾👏👏👏👏👏👏

[@RegWestly]

yes please

[@paullavender6227]

Great video, thank you. P.

[@earlmcnulty4665]

I absolutely LOVE these technical videos. Keep em coming!!!

[@kardnails8729]

When you were comparing the 50mm and 25mm at the end, why didn't you divide the F stop by two as well?

[@gxvro1]

I'm a physics student and also photographer, and seriously, this is by far the best and most accurate explanation about DoF I've ever seen on an accessible medium

[@geraldundone]

Thanks so much, Gabriel! That means a lot coming from a person with your background.

[@millerman2133]

seriously. (im no physics major lol) of all the articles and books I've read, this video is the most technical, yet understandable way of explaining DoF. why couldn't I find this video a year ago?!

[@vincenzodellama7158]

@@geraldundone what about compression of the background and distortion? Shouldn't the background look closer and the lens have less distortion the longer it is?

[@JordanDanielWende]

Vincenzo Del Lama While not addressing distortion he does talk about compression at the end of the video and shows examples with the DoF calculator (the woman in front of the tree)

[@ariesmight6978]

You beat to me to posting. A nearly exact same response.

[@jamesbartoschsr.9474]

I am 71 years old and been doing photography since I was 8 years old. I have taken multiple classes on photography and you have been the only one that has explained DOF clearly. Thanks...

[@rossthomas4738]

Gerald you need to be invited on other photography channels to once and for all explain this subject. Undisputed the best explanation on this subject EVER. You impress me more each video.

[@Noojtxeeg]

This was much better explained than a lot of other videos out there.

[@geraldundone]

Thanks, mate! Cheers. 😃👍

[@ChocoLater1]

@@geraldundone People who talk about it don't understand it at all obviously.

[@MeAMuse]

The first video on this subject that has not got a million angry people angry writing comments. I would say thats a big success. Good job!

[@geraldundone]

Haha. That's a fun way to look at it. Cheers! 😃

[@radialbladeworks6183]

My god, man. You clearly have an absolute grasp on the subject matter. Not only this, but you have the ability to conversationally explain the material. Finally, you identify common issues and misconceptions, indicating an awareness of the general community’s perspective. This is top tier teaching. Fantastic video

[@5050-Films]

I’ve been doing photography for 40 years and am an engineer - this video and your video on f-numbers are hands-down two of the best photography videos I have ever watched. Keep creating sir!!

[@johannbauermeister3916]

Wow. After decades of photography, I find out I had an incomplete understanding of this. Thanks!

[@overnightdelivery]

Great explanation. If you get confused by the math and numbers, simply skip to 13:42 because that's all you REALLY need to know. The main difference between M43rds and Full Frame is 2X Crop and 2 Stops of Light.

[@herrchristophotto]

Thanks a lot for finally giving a good and clear explanation of these relationships. Most people all over the internet are like: larger sensors produce shallower depth of fielp per se. Which, in my opinion, is plain rubbish. Point is, you're basically using longer focal lengths to achieve an equivalent field of view with larger sensors. Hence, you're automatically getting shallower depth of field using the same f-numbers. E.g. 50mm f4.0 gives you a shallower depth of field than say 25mm f4.0 for the same focal distance. That has ABSOLUTELY NOTHING to do with the sensor size but ONLY with the basically longer focal lengths you're using. Thanks for finally making this clear on the interwebz :)

[@matteogiordano6166]

Straight question: same lens, same focus distance, same aperture and different sensor size. I should have the same depth of field and different field of view, I thought. But it's not! Why? Please help, my mind is melting. I have used DOF calculator: 100mm lens, f5.6, subject/focus distance 5metres; then I switch from FF to micro4/3. Result: the micro4/3 has the depth of field half shallower! What am I missing??? Since a sensor is just something the captures an image, how can it on earth have something to do with the depth of field?

[@jeffparkin3122]

For years I've been looking for a video like this that concisely explains to my college students the interaction of DoF, sensor size and focal length. THANK YOU!

[@Ram.Saketh]

While there are only two primary factors that affect "depth of field" in photography, there's only one primary factor that increases "depth of knowledge" and that factor is Gerald Undone! 😃 Here's a super thanks to tell you how much I enjoyed watching and learning from your video.

[@whoismatt]

Really loved this explanation dude!

[@geraldundone]

Thanks a lot, Matt! Means a lot coming from you. I really enjoy your videos. 😃🙏

[@geraldundone]

Do you still not have Twitter though?

[@whoismatt]

@@geraldundone @whoismattj but I'm rarely on it haha

[@krzemian]

Lol, 40 minutes ago I was playing a guessing game on which thumbnail to click for the long awaited explanation of DoF contributing factors, aperture, light, shit like that. I'm glad I ended up with you as the teacher. I appreciate the down to earth, no bullshit just-enough-scientific explanation of these complex subjects. I wouldn't likely consider them that complex had I slept more than an hour today, but hey, you gotta roll with the punches. Will definitely revisit these with a fresh pair of brain hemispheres in a while. With that, if you like my comment, make sure to keep making these technical explanation videos. If you don't, please make a revenge on me by making them twice as often. Thank you.

[@KruiserIV]

As always, great video. Concise, accurate and informative. Something I've noticed is that the more frame space my subject occupies, the more thin the depth of field appears to be. For example, if I photograph a person's upper body with a 105mm lens at f/1.4 and their body occupies 50% of the frame, I can achieve the same apparent depth of field using a 35mm lens at f/1.4 as long as I move the camera closer to my subject so that their upper body occupies the same 50% of the frame. So, I can use my subject's size, relative to the frame, plus my f/stop, as a rough yardstick to measure the perceived DOF.

[@geraldundone]

Yeah, definitely. That absolutely works!

[@stumpyjock]

What a fantastic explanation of dof. Loving your work Gerald, these tech orientated videos that you produce absolutely rock!

[@geraldundone]

Thanks, Steve! That's a really nice comment. Much appreciated! 😃👍

[@JSicking]

I've struggled to understand exactly how to setup my portrait shots to get the Depth of Field results I'm looking for. I'm so thankful that I happened to stumble onto this video in my search as it's easily the most straightforward and helpful explanation I've come across so far.

[@cliff9101]

That DoF simulator is so helpful and explains the relationship between all these factors (crop factor, aperture, distance to main subject and how far away the background appears, quality of bokeh, etc) in such an easy and intuitive way. It's also helping with my next lens decision. Thanks!

[@edma22]

So glad I came across your channel! This is the single most useful video I've some across about this subject. I've tried to wrangle DOF as I switch between 35mm film/sensors and up to 6x6 and 6x9 film backs. I'd figured out the focal length equivalency but struggled with the way DOF was changing. Suddenly, the circle of confusion I had about the subject, if may apply a weak pun, has resolved incredibly sharply! Thank you for your sterling work.

[@geraldundone]

Haha. I chuckled a little at the pun. 😃

[@borderlands6606]

The clearest explanation I've heard. Especially the part about the photographer not moving position at 9:44

[@geraldundone]

Thanks so much! I'm really glad to hear that. Cheers 😃👍

[@borderlands6606]

Gerald Undone something I'm not clear on is the onset of diffraction relative to lens size. So for example it's generally accepted that diffraction becomes evident on full frame lenses with an aperture smaller than f8. Diffraction is a by-product of iris diameter - the smaller the "hole" the more light waves bend or deflect. However if I want a deep DoF for street photography, will diffraction become less of an issue on a small sensor camera because I'm using f5.6 rather than f11, and is the entrance pupil a constant in diffraction? I hope that's clear.

[@geraldundone]

If I'm understanding you right, my answer would be that diffraction is still a concern and is scaled in the same way most things are with full frame to m43 (by a factor of 2). So, if you're experiencing unwanted results at f/16 full frame, you'll get similar results at f/8 on m43. Assuming build quality, etc. is similar.

[@borderlands6606]

Gerald Undone Ok so diffraction onset is a format variable not an aperture constant. That makes sense. Thanks.

[@FlammBii]

Every time there is something i don't understand, i come back to this video and turn your points in every direction in my head and i find an answer to my question Thanks man

[@dudenamedskip]

I've never understood the crop factor when using a matching lens for a smaller sensor until this video. 35mm is 35mm but the FOV gets more narrow on MFT which causes you to stand further away than a 35mm FF. Seriously, thank you for always making things so dang clear and easy to understand.

[@TonyMacina]

Finally, a well articulated explanation! I'd been trying to tell people this when I mentioned looking at a GH5s instead of a full frame camera for short films. With a plethora of decent manual focus lenses like the Voigtlander range at f/0.95 and the Veydra at T/2.2, most needs are met by M4/3 for narrative video work.

[@MrRlaureano]

You should be in the science field Gerald! :D That was the best explanation I've ever heard, seen or read regarding DOF. I really appreciate learning the "science" in photography, which is indisputable, compared to the art in photography, which is subjective. The fact that you add motion graphics makes watching your videos not only entertaining but also very educational. Excellent work!

[@geraldundone]

Thanks, Robert! Appreciate your kind words. I'm glad you like the graphics. They're the most time consuming so it's good to hear that they're worth it. 😃

[@RangelCostes]

This is literally one of the few videos that CLEARLY illustrates what's going on. Thank you SUPER helpful, keep up the great work 👍

[@dennisjones5579]

This is by far the BEST video/explanation of DoF I've ever heard, and I've been a photography hobbyist for > 40 yrs. You rock sir!

[@jumopellicano]

You re absolutely the best tutor in youtube. Congratulations for your beautifully explained topics

[@nowornever2504]

Just watched “What is undone video.” Undone...thorough but easy to understand at the same time. “Effectively informative and comprehensive”

[@therealcoolio3267]

Indispensable guide on my journey to understanding all of this. Truly a knack for making complex ideas easier to understand. Here’s a giant thank you!

[@PeterLavender]

Helpful?? Oh my gosh, it was brilliant. You really have a knack for explaining the concepts without treating the audience like dummies. Thanks Gerald.

[@mattdustz9215]

Man there is no other source on this platform (all big ones included) than can explain things this sharp. Thank you.

[@martinwillis8015]

I agree with most of the comments here that this and the other 2 videos are very informative and well explained even for a reasonably complex topic. What has been mostly refreshing is the comments that have been made. I have seen many other you tube content producers try explanations on the subject and the comments section turns into a bun fight. The quality of your content is clearly far superior as are the quality of you viewers it seems (hopefully that includes me!) so for that i congratulate all here. fabulous channel and that seems to attract a good group of followers.

[@geraldundone]

Thanks, Martin! I agree, we've built a quality community here. Cheers!

[@MichaelWootten]

I’m so glad I found your channel! You’re out here proving REAL and SCIENTIFIC information! You’re speaking the language of professionals. So much good stuff in this video, but a huge nod to dispelling the myth that a larger sensor inherently gives you more depth of field.

[@geraldundone]

Thanks, Michael! I'm glad you found the channel as well and that you're enjoying it. Cheers!

[@petersigma]

I think the focal "plane" produced by the lens, is actually a bit curved I think ( even with aspheric lenses). So a larger sensor ( assuming its flat) would tend to have that curve of the " focal plane ) it would have more distance to pull away from this curve. I understand your video, but I think it practically confuses the issue. Wide lenses effectively do have deeper depth of field than longer lenses. With a parafocal zoom lens you can zoom in on your "subject" and focus with the focus ring, and objects behind will go out of focus, when you zoom out to a wide (short) focal length, the depth of field expands and the background comes into focus. Also... f numbers are representative approximations of a complicated math formula... en.wikipedia.org/wiki/F-number @@geraldundone

[@espirite]

A true genius is someone who can explain complicated concepts in a way that others can understand. This was the first time I've seen such a clear and concise illustration of this concept.

[@geraldundone]

Thank you very much! That's a huge compliment. Really appreciate it.

[@georgedavall9449]

First of all, Thanks for this very clear and correctly explained video. Late comment here, but HUGE THUMBS UP for @ 0:59 ! So many people get this, and DOF wrong. Yes, there is only one true plane of focus, but I constantly see Content creators stating, “ I had everything in focus from this rock to that tree in the background,” and so on and so forth… ( Yes, a Pet Peave of mine. ) Age of Digital seems to have made for some lazy Photographers. I fondly remember my Film days, of lenses having manual aperture rings along with the DOF scales on the lenses. I learned to ‘approximate the DOF’ by both the lenses, and by the ratio that called for DOF to being roughly 1/3 in front of the plane of focus, and 2/3 behind. There are of course variables in all of this. Well Done, Gerald Undone! 👍✌📸 😉

[@snxoppick]

Finally the best explanation about this topic, especially when you make side by side pictures with different focal leght but same depth of field. That things make me confuse sometimes. This video pure gold! Thanks Gerald. 👍

[@khuo0219]

I have always been confused about the so called lens compression. Your explanation about the longer focal length magnification clears things up.

[@cameronreynoldsRPV]

You entertained me with magic tricks for 14min. Honestly though, when I handle my gear I feel like I feel a lot better knowing how everything works. Makes me have a sense of security and understanding where I can have fruitful results. Beyond thankful for this channel!

[@andrewelder2739]

I appreciate the breakdown (even a few years late to seeing it). I've heard conflicting reports that the area of focus is actually weighted toward BEHIND the focal point (30% in front, 70% in back), but it looks like you're proving that it's a lot closer to 50/50!

[@Luke-pi2nq]

I am in shock. What might have been a possible clickbait video is actually the most genious explanation for understanding the depth of cornfield and now I can calculate whatever the f*** I need from this point on. Thanks to this master.

[@FilmmakerIQ]

Late to the party - but there needs to be addition of magnification to the direct attributes to depth of field. In your discussion about what's acceptably sharp and what isn't you left out how we make that determination. When you magnify something more, your ability to detect whether something is in focus or not is increased (that's why the zoom in feature is used to set critical focus). Magnification takes place both in focal length and sensor size - with the interesting caveat that smaller sensors have inherently shallower depth of field!

[@yuvrajwadhwani]

Interesting point

[@lefthandright01]

You seem fairly confident in your knowledge, so it should be no surprise what I'm about to say. I met an optical engineer and ask their opinion on this and their was response was, "What photographers know as bokeh is a lens quality and not a sensor quality. You achieve the same affect on any sensor, you just need to change the 2 direct and 3 indirect variables. Iris size, distance subject, magnification, focal length, aperture." In their opinion, aperture is one of the three indirect factors. Typically speaking, the larger the sensor, the bigger the lens. The bigger the lens, the bigger the iris. The longer the lens, the greater magnification factor. The bigger lens just lends itself to the task, but it can be replicated multiple other ways.

[@savnac]

This is the best explanation I’ve seen so far on KZbin for this. It’s the only one that really allowed clarification for this misconception to “click” in my head. Thank you so much! You really explained this perfectly.

[@geraldundone]

Glad to hear it. Really appreciate your comment. Thanks for taking the time! :)

[@ashleybowling4006]

SERIOUSLY thank you for this!!! I got SO SO frustrated the other day because I couldn't understand these concepts or find anything that explained it well enough. LIFE SAVOR FOR REAL, THANK YOU

[@TrevorMcGrathPhotography]

Came across your channel when researching videos on A73. This is my third vid of yours I've watched and reading comments the word "Genius" has been mentioned...I agree, it is possible that you are one! You not only recorded a video on HDMI cables but also made it interesting.

[@shaun8666]

Superbly explained, it melted my brain a bit trying to keep up ha. I think you explained this far better than other popular photography channels who I dont feel are as passionate about photography, they just do videos. Good work :)

[@geraldundone]

Thanks so much, Shaun! That's very kind of you to say. Cheers!

[@dinoschachten]

Beautifully explained. I had thought about this a lot, but not considered that it really only comes down to two factors. Another weird thing people tend to do is claim that full frame equals shallower depth of field, which again is a compensation thing because people would typically use a 25mm on M43 where they would use a 50mm on full frame (and at the same f-number, the pupil diameter of the 25mm is what they usually are on wide angle lenses: small), but at the same time you can argue that the same lens produces more bokeh on the M43 because of the magnified blurry bits. Which I guess shows that how much bokeh you achieve on each sensor size really depends if/how you compensate. I love how people on forums use both arguments to have it their way.

[@yazid222]

Gerald, Let's consider all the light rays that enter the lens coming from a single point on an object that is in focus. They converge after entering through the lens, of course, and the point where they converge is on the sensor (since the object is in focus). In your illustration, 4:35, the rays diverge again and then form the image of the tree on another plane. In fact those rays do not produce the image of the tree, but one single point from the tree (which is our in focus object) An image of the tree is formed because every point on the tree that is lit reflects light that converges exactly on the plane of the sensor. On the sensor, then, all those points form the image of the tree (flipped both horizontally and vertically) Thank you for making the kind of videos you make. I appreciate your style.

[@alantuttphotography]

Finally! Someone who can properly explain the relationship between the various factors. The only thing that seems off to me is the DoF calculator showing almost equal distance on each side of the subject being in focus. I always learned that 1/3 of the DoF was in front, and 2/3 behind the subject.

[@Cuetips1000]

Very good explanation. 9:56 The dof (section where all is sharp and in focus) is the same, but the bokeh (section out of focus) is or looks different. For me, the photo on the right looks more aesthetic than the left one. The left photo shows more and smaller details in the background, and therefore more and smaller blurring circles. Because of this effect, the human eye is cheated and discerns a crispier pic, even though the mentioned details are blurred. For me, the bottom line is: Ceteris paribus the focal length does not affect the dof but it does affect the bokeh.

[@johngwheeler]

This is by far the best explanation of the subject that I have seen. I thought that I knew just about everything about this, but I’ve learned something new -I’d never consider entrance pupil size before. Great stuff!

[@geraldundone]

Thanks a lot, John! Appreciate that.

[@JonnyHavens]

I swear, every other gear channel on KZbin just recycles old info and may or may not fact check first. Gerald actually puts the work in to give us new stuff and I really appreciate it!

[@ginatinyverge9661]

Man... this channel is overloading my brain with valuable information.

[@TheHeesin]

Epic! I'm getting drawn into watching your tutorials. They're no nonsense "this is how it works" stuff and you show why. Like it!

[@geraldundone]

Awesome! Glad to hear it. Thanks for the comment. 😃👍

[@EnterSpacebar]

You're an excellent teacher Gerald. Although I learnt nothing new in this video, I thoroughly appreciate the effort and how well you put it all together. A lot of people will find these explanation videos very very useful. Thanks for making these excellent videos. You truly stand out among all the photography KZbinrs, one of the counted few really worthwhile photo/video channels out there. Keep going!

[@geraldundone]

Thanks a lot! That means a lot. Appreciate it.

[@EnterSpacebar]

@@geraldundone You deserve it man. Your research and the effort you put into making these videos shows very clearly. Big respect 🙏

[@sonicsaviouryouwillnotgetm6678]

this is by far the best explanation on the subject that I've come across. It might flat out be the best video that I have seen from you, peroid.

[@geraldundone]

Thanks so much! That's a big compliment. Really appreciate it. Cheers!

[@michaelmazzen]

Pretty much the best way I've ever heard anybody explain this stuff... Im totally going to steal this next time Im explaining this to my own students :))

[@benharris3949]

Brilliant! I finally understand this. Thanks for taking the time to break it down into primary and secondary influences, that makes so much sense. And I finally understand the relationship between sensor size, aperture, and dof. Thanks for a such a helpful video.

[@geraldundone]

Perfect! That's exactly what I wanted to hear. Thanks for letting me know it helped. Cheers! 😃👍

[@micahramsay3341]

You are legit a god at explaining things. This is the first complete explanation of DoF I have seen on KZbin so thank you and keep doing what you're doing.

[@wizrom3046]

I just watched some videos from people who had no idea, but pretended they knew what they were talking about. Like saying that the same lens on FF sensor gives more bokeh than the same lens on Crop sensor so you need to have larger aperture on Crop (by crop factor). It's obvious that the lens properties and distance to target makes the bokeh and whatever sensor or piece of paper/film etc you stick behind that lens doesn't matter. Anyway, well done on your explanation. Gerald Welldone. :)

[@RegWestly]

You are very good at explaining this subject in a clear and simple way. Well done! Your examples and style work very well

[@MatthewF21]

Hey thanks for linking the dofsimulator webpage! It helped me a whole bunch to visually understand what the depth of field looks like with different types on lenses on my camera

[@luizarroyo988]

This video is awesome! Gerald, you are quickly becoming my favorite KZbin channel. These explanations are tremendously helpful.

[@geraldundone]

Glad to hear it, Luiz! Thanks for the encouragement and kind words.

[@scottmilholland176]

I've watched lots of videos on this. This is the only one I've seen that actually properly explains it. Thanks!

[@19meric19]

Because of your magic tricks, I immediately subscribed. Love the creativity and humor, thanks!

[@geraldundone]

Awesome! Thanks so much. Always glad to have a new subscriber!

[@DiversReady]

Another great video. I learn so much from this channel. Thanks Gerald.

[@cesarporrello164]

the best explanation EVER! for these reasons I always say so... more technical language is needed in all photography courses

[@ononearts]

Very helpful, well explained as usual. As you said, there are too many sites with erroneous and conflicting explanations for the mechanisms of depth of field, most notably those trumpeting shallow depth of field as only possible with larger sensors - not helpful at all, and easy to discover as untrue with further experience. Little Ah - Hah moments made me want to know more about the science behind it all. Thanks for another step in that direction! 😊

[@maticmirkac6653]

This along with your other videos were the most insightful bits of info that I have come across during the past two weeks of research about what camera to buy. Thank you for sharing expert knowledge and for mentioning the DOF simulator, it's a fantastic tool.

[@BigMilan]

Wow! I love this type of thing. I notice a number of things in photography terminology have been made up by people who don’t fully understand how the related physics work, but this one never occurred to me either - thank you very much for this video! Subscribed!

[@martinjohnston4274]

This is one of the best explanations I have yet seen on this topic and the on-screen graphics help a lot. Pleeeeasse, could you slow down your delivery a bit? It's exhausting!

[@manchumuq]

The clearest and most precise explaination of the century's most meaningless debate, ever.

[@simonpeck]

Fantastic explanation! You hit all the right points in the right order with helpful illustrations and no fluff.

[@jacknicholasny]

You and the Maven are the best camera tech guys hands down.

[@DJLsbVapes]

What an awesome and perfect explanation...

[@geraldundone]

Thanks, mate! Much appreciated. 😃👍

[@muhammadobaid7500]

Woooow , just wow ! I've been studying and working in this domain for more than 10 years.. However, this video, believe it or not, made me stand up and clap ! I can't say thx enough Gerald !

[@DJSkippy]

Excellent work! I'm so glad I happened across your videos! I love they're so much more in depth and technical than most other videos!

[@geraldundone]

Thanks, Logan!

[@0ecka]

I'm just glad that there are smart people like you making this kind of videos, instead of spreading ignorant nonsense. Thank you very much! But it's not even about the depth of field. It is about the amount of light used to create an image. Depth of field is simply a side effect as well as an indication of the light gathering ability of the lens (the entrance pupil) or the camera settings used for it. Those two, the DoF and the amount of light transmitted through the lens, are inseparable (in comparison under given lighting conditions, of course).

[@iditriza9708]

Everyday I’m just amazed with the level of knowledge, information and experience is being delivered for free on youtube. One of the best subscriptions I made! ✌🏼

[@geraldundone]

Thanks so much! I'm happy you subscribed too. 😃

[@jjdawg9918]

2 years later, still the best explanation on the subject and I really don’t see anyone ever improving on it. And after seeing this I so wish that the person that came up with term Depth of Field would have tried to be less cool with their terminology and just used the term Depth of "Focus". To a beginner the term "Field" can easily be confused with the magnification, or apparent compression between the foreground and background(telephoto effect)

[@FilmmakerIQ]

Depth of focus is actually the term reserved for the back of the lens - it's related to backfocusing the sensor to the lens.

[@aiquelindo]

Gerald, thank you for the excellent presentation. There are many professional photographers and self proclaimed experts out there who should definitely be watching this! Keep up the amazing work.

[@Photographicelements]

Magic tricks!! (I don’t know what all that other stuff was). Haha, very detailed explanation, thank you; I wish the rest of youtube could understand this. Brings me back to when I would focus pull, hinting to the DP for a wider lens and higher ap, just to make my job easier. Yes, depth of field calculator app really does help. This is actually the best explanation I’ve heard, & all consolidated into one, nicely done Professor G.

[@geraldundone]

Thanks! I figured you'd like the magic tricks. 😃

[@Photographicelements]

Gerald Undone never cease to amaze👍

[@bonsaimediahousetx]

your prowess for explaining scientific science stuff, passion for the field and cheesy yet adorable jokes have given you away. you were clearly a 90s kid who grew up on bill nye the science guy.

[@geraldundone]

I was born in the 80s (1985), but I'm definitely a product of 90s pop culture. I sure did watch a lot of Bill Nye. I'm glad you like the videos! 😃 Thanks for the fun comment.

[@tysonator5433]

A lot of information to process, again Gerald explains is a concise, clear manner. Well done mate

[@geraldundone]

Thanks, Tyson!

[@michaelstewart579]

This was really well done! Good to hear from someone on KZbin who truly understands how DOF works and can explain it. I hate to nit-pick, but I will anyway because something like this should be 100% correct. Shouldn't you're diagrams all show more DOF in front of the plane of focus than behind?

[@Jones411c]

Dude, excellent video. Clear explanation of DOF. You should have been my teacher in the past. Learned it completely wrong when starting out. Only by learning along the way and testing stuf myself did I know my info was wrong. Keep up the good work! ;)

[@geraldundone]

Thank you very much! Happy to hear the video was helpful. Cheers!

[@EmilFromFilm]

These videos are so amazing Gerald. My brain hurts a little bit and then I start to get it. Feels great that I actually understand the physics of my photography.

[@geraldundone]

Awesome! Thanks for saying so. I'm glad. 😃👍

[@monky9000]

First, let me say that this video is one of the more clear and concise ones that I've watched on this subject. This isn't a trivial subject for anyone without a background or interest in math or optics (or a combination of both), but the explanation here is well done. That said, I don't agree with the statement that DOF depends only on the distance to the subject and the entrance pupil. Here's why (fair warning, I'm nowhere near as good at explaining things clearly as you are, which is why you make videos explaining things clearly, and I don't): Let's start with depth-of-field itself: DOF = Near point in focus - far point in focus To determine the near and far points in focus, you need to know the focus distance itself and the hyperfocal distance. The former is easy enough; you know that when you focus your lens. The formula for the latter includes 3 terms: the f/number of the lens, the circle of confusion's acceptable diameter limit (COCADL), and the focal length itself. So to recap, we now know that DOF is dependent on at least these things: entrance pupil diameter, subject distance, focal length, and COCADL. The important one here is the acceptable limit for the circle of confusion. You alluded to, but did not name, this term in the text box at 5:00 in your video. The reason this term is integral to our discussion here is that it is *dependent on the final displayed size of the image*. There's all sorts of writing out there about this number, and how to arrive at it, and how intertwined it is with print size and the "average" human vision, etc.... but for the purpose of discussion here, we can assume that for an image displayed at 8x10" from a 24x36mm (i.e., "full frame" or 35mm film) projected image, the standard value of .029mm works. All that aside, the main takeaway for this context that it is related to the size of the final image, whether it's a print or on a screen. So, in simpler terms, this means that the DOF *is* in fact dependent on: - the entrance pupil diameter - the subject distance from the lens - the focal length - the final image size The subject distance, focal length, and the final image size can be combined to simplify this statement in to what I feel is the more correct statement: Depth of field depends on only two things: 1) entrance pupil diameter, and 2) the final magnification of the subject to the displayed image. Interesting side note: the reason that your demonstration of magnifying the background worked is because of the convoluted math here. When you approach the subject and use a wider lens, the subject still has the same magnification, but the background does not (you see more of the background, because of the wider angle of view). The depth of field, at the subject, will still be near identical as you saw, but despite this, the background will look less blurry. This adds to the confusion - some people mistakenly assume that this means you have more depth of field (as you demonstrated, the DOF is actually the same). After you isolated and magnified the background, you brought the final magnification term back to parity for that portion of the image. I'm sure I've made this unnecessarily convoluted (and it's been a very long day, so it's possible there's a typo or other mistake in there somewhere), but hopefully you find it useful. I can explain further and walk you through the whole formulas if you have any questions.

[@geraldundone]

I agree with your comment. I made a pinned comment when I posted this video explaining that the focal length side of it is even more complicated than I explained and tried to elaborate a bit on the importance of magnification. I completely stayed away from the delivery image size, because I was worried I would go on a tangent about print distance and resolution of the eyeball. It's hard to balance a reasonable explanation for a KZbin video with being 100% accurate in every detail. My original video was about 55 minutes long! No joke. Anyway, good comment, good points.

[@monky9000]

*facepalm* Sorry, totally missed that. My bad. LIke I said, it had been a long day :)

[@mattstout804]

I’m pretty sure this is the first time I’ve seen a photography channel reference the DOF simulator. Great job on this, I found this very informative. I found this to one of the most useful tools to understanding DOF. You can also use the “lock field of view” box to keep your framing the same automatically. The developer Michael works off PayPal donations so hopefully this drives him a little revenue to maintain and develop further.

[@geraldundone]

Awesome! Yeah, it's a fantastic tool. Really well put together. I recommend it all the time. Thanks for the comment. Cheers! 😃👍

[@darlingtoncd]

I agree. I've used the DOF simulator for some time and re-visited it to compare the differences in Camera sensor sizes etc. It's important to understand the principle of what's going on, as too many photographers on KZbin are biased or like to focus on a certain explanation that reinforces their prefered interpretation and can leave some people (judging from comments) miss-informed as to the whole 'picture' (elements) that play a part in DOF. It's simple enough in principle and people can then make choices based on whatever they want to do - with choice of camera (system/size) and lens choices...then just enjoy taking photos :)

[@metasploitstudios2257]

Thank you very very much. I've had this doubt for over a month now and doing research on it. I recently saved up and bought the Sony a6400 body. I am currently saving up for the Samyang 135mm 1.8. However I was worried that I might not be able to enjoy that 1.8 in my photography. However, with the use of that app, I've been able to compare what I'll get it I go for an 85 instead or a 135. Your explanation made lots of sense and my physics background made me understand you very very well. I can't thank you less. I'm now looking forward to saving up for my first lense. Photography in my country is still at it's infantry stages. With a 135 I will stand out drastically. Since I'm more of an outdoor photographer.

[@iguanaman08]

Hi. Just subscribed to you after watching this! Been a amateur photographer for years and never really understood how to calculate DOF. Your explanation and using the DOF simulator has been a lightbulb moment for me. Thanks so much!

[@martingranger40]

Good video - covers so much, mind blown....will have to watch 8 more times to fully comprehend it. Thanks for making it!!

[@ErikHill1]

Ugh finally someone put together a proper video on this subject! Thank you!

[@AlexZavalny]

Hate leaving comments, because I hate typing, but man this channel is gold. I thought I was nerd, before watching it, now I know I am complete noob. Excellent video, excellent explanation to old topic which everyone says is easy but almost nobody truly understands. Thanx.

[@geraldundone]

Thanks for taking the time. Appreciate your kind words. Cheers!

[@DONNYLAI95]

One of the best scientific DOF explanations ever...

[@r14557]

so glad I found your channel, Gerald! Makes me wanna do my own "photography courses" videos. Amazing work

[@geraldundone]

I'm glad you found it too. Thanks for commenting.

[@nomancave591]

This is the first video on the subject that I understood with one viewing and also made sense.

[@andyrechenberg]

Such a great instructional video. I love deep diving into information and this was incredible. Gonna forward this one to all my creative geeks. Thanks!

[@geraldundone]

Thanks so much! Appreciate the kind words and the share. Cheers!

[@stevenroberts9172]

This is the best explanation I have seen on this subject and makes sense in real world practice. Awesome work as always Gerald :D