Focusing on Depth of Field and Lens Equivalents
ฝัง
- เผยแพร่เมื่อ 17 ม.ค. 2016
- Please consider supporting us on Patreon: / filmmakeriq
How much space in front of the lens will be in focus? That question defines Depth of Field - but this simple concept has lead to a staggering amount of confusion in today’s multi-format camera environment. Through some fundamental scientific demonstrations, we will clarify concepts like circle of confusion and lens equivalency.
Take the full Filmmaker IQ course on Depth of Field and Lens Equivalents with sauce and bonus material at:
filmmakeriq.com/courses/focus...
If you have any further questions be sure to check out our questions page on Filmmaker IQ:
filmmakeriq.com/balcony_categ...
ERRATA
The ISO in regards to Lens Equivalents should be multiplied by ISO^2 because we're dealing with two dimensions not just one. Multiplying by just the ISO will result in slightly darker image (as see in the demo)
Some people have jumped to the conclusion that the Circle of Confusion is the Pixel Size. The CoC is LIMITED by the Pixel Size in that it cannot be smaller than the pixel size, but in most cameras the pixel size is much smaller than the CoC (or at least by a standard CoC that calculators use for determining depth of field). This explains why a Full Frame 12MP camera will have the same DoF as a 50MP camera. But if you enlarge the photo enough, eventually you will be able to see more detail in the 50MP image which less of what looked in focus in the 12MP image will actually be in focus.
Some people have commented that the video is a bit soft... when I'm large in the shot, it does indeed look soft - when I'm shrunk down, the video looks sharp. The lens has not changed - only the magnification of the image. This is a very real analog to what's happening in smaller sensors - when a small sensor crops in you can see better detail and it looks soft, when captured by a full frame, the image looks sharp. Therefor smaller sensors (given all other factors equal) have a shallower depth of field.
i freaking spent thousands of dollars at institutes and they could not teach me any of this properly, you teach everything millions time better and also for free !!! love your videos man, keep it up :)
Even if I could afford to go to film school I would probably fail. I have always been a slow learner. So I've always taught myself or if someone could teach me hands on. I could understand stuff faster. With John's teachings. I maybe have to watch his video maybe 3 times and I understand what he is saying. I love it.
This is so true. I've been studying film production for 3 years now and nobody ever explained to me this so didactically.
Photoshop Tutorials | Photo effects impactguru.com/s/uxZ0zQ support us donate
This is because this person is a true TUTOR and a true TUTOR teaches everything keeping in mind Education as a Mission and Not as a Business
yikes
This is one of those videos i regularly come back to watch...
Nicely done! I'm glad to see these concepts are becoming more widely accepted! Even just a year ago, this was a really controversial topic. I'm constantly switching between 35mm, Super-35, MFT, and BlackMagic's mini-MFT sensor sizes for video, and this math has been critical to choosing the right lenses and settings for different scenes.
Hi Tony! Your video changed how I perceived sensors size in relation to DoF. I really had to work hard to wrap my mind around it with physical experiments. There was a lot of myths that I needed to let go and at first I was hesitant to discuss this topic because of the confusion it can cause. But after I dug deep enough, I felt I could explain it my own way.
Anyhow, Thanks for having the courage to stand up against an often ornerly photography crowd on this subject :)
Tony & Chelsea Northrup i am confused here, please some assistance: 2x crop factor on focal length for a 50mm 100 (2x 50); 2x ISO is ISOxcrop factor^2... ISO 160 x (4) 640. But... what about of 2x aperture for f/4 is f/8 (2x8) or f/5.6 (as 2x(f/4)=f/5.6).
It's a straight multiplication, not taking in consideration of stops. So 2*f/4 is f/8
mr john: i really really appreciate your fast answer. So the four cases ( focal, focus, aperture and iso^2] are straight multiplication
Focus does not change. Remember these are equivalents... What would be the equivalent on a full frame sensor.
This type of videos are like The Bif Short of Internet.
You don't understand the details, but you understand the big picture, and that's the most important thing and the most difficult thing to explain. Well Done Filmmaker IQ.
As usual, fantastic stuff. Personally, I love the in-depth coverage - sent many a person over here when they have questions. Thank you.
Kevin - The Basic Filmmaker impactguru.com/s/uxZ0zQ support us donate
Thank you! After all these years... I never realized that crop factor effects *everything*, not just "equivalent" focal length.
This is seriously the best video on DOF and sensor size in the world.
Your videos are amazing and every photographer should watch them!! Wonderful explanation!! :)
And this concludes as the only valid demonstration of DoF, focal length and crop factor hysteria on YT. Thank you for a coherent and scientific explanation!
Brilliant! Kubrick would be proud. He was obsessed with tack sharp images.
Finally somebody who knows and explains the subject very well not is not from the manufacturer side(who wants to market us).
This was BRILLIANT... your demonstrations and re-wording of the concepts in multiple ways makes the concepts more easily accessible to everyone. This is quickly becoming a favourite channel--thank you so much for taking the time to do this!!!!!
"I can see clearly now" ...... Thank you Mr Hess for this sweet video! I love the work done on this channel!
I'm so happy every time you upload a video that I thumbs up it within the first couple of seconds.
YES!!! FInally a video where it is said that smaller sensors give actually a shallower DOF, if all the other variables are the same!!!! FINALLY!!!!
That's not correct because the scene composition is the most important variable.
The field of view is the most important factor because the entire point is to create and image of a given THING. The field of view can't possibly be the same if the other factors are.
Think about it, when using a camera, its to photograph something, right? The subject is the reason for the photo, not the camera's settings. If the field of view is different, then that "something" is not the same. Therefore, for a given field of view (with matching, lens, aperture and ISO) the larger sensor will have a shallower depth of field. He says this at 15:48
Yes it is... it is an apples to apples comparison. it's just different which apples you want to compare.
@@FilmmakerIQ
You may be responding to an incomplete comment. You wouldn't mind looking at what I wrote above and confirming if we have the same understanding, would you?
TH-cam is so screwy it's only showing me the most recent comments. It's not even showing your earlier comment. Basically everything in the video is correct. Same focal length same aperture... the smaller Sensor will have a shallower DoF AND a smaller FoV
It is @@FilmmakerIQ.
I was speaking to what the commenter mentioned saying that for a given field of view (with matching, lens, aperture and ISO) the larger sensor will have a shallower depth of field as you mentioned at 15:48 or so.
I just recently came across your page. These concepts are explained pretty well.
All your content is superb, but you went to even greater heights with this one.
You truly are the master of the photographic math!!! I really enjoy your show, as there isn't anyone else out there (that I am aware of) who explains the math and logic behind all the aspects of photography that well!! Keep it up!!
Filmmaker IQ is always solid content! Thanks John :) The whole depth of field discussions will never stop. There are 2 ways to compare it both are right both are opposite :)
+victorbart Not sure what the other way is, but this is the right way :P
+Filmmaker IQ I am still confused. I don't understand how the depth of field calculated from the pixel size is related to the depth of field coming from the blurred back lights (or so called bokeh).
Go back to the animation of the single point of light. If the point is in focus (6:08), it will be a point in the final image... Once it goes out of focus, it becomes a ball of light... Just like bokeh... The bigger the spot, the more out of focus it is.
+Filmmaker IQ This is clear. But my confusion starts at 13:50 when you talk about bokeh of out of focus lights. Their sizes will not depend on the pixel size, they will depend only on lens focal distance and aperture. So everything you say after 13:50 using crop factor, focal length, field of view and aperture is clear but I cannot relate it to the pixel size and circle of confusion.
Let's say we have 2 full frame sensors, one with 12mp and another with 48mp resolutions. If we use the same lens with same focal length and aperture settings we will get two pictures with identical bokeh even though 48mp sensor has the shallower depth of field.
+Zuriah Heep The problem with your paradox is you're comparing apples to oranges ;)
Two prints - one from a 12MP one from a 50MP camera, identical dimensions. They look identical right? What's the difference between the two? The Pixel Density. The pixels are much smaller on the 50MP than they are on the 12MP. But that's cheating ;)
What happens when you match the pixel density - so that each pixel from the 12MP camera is exactly the same as the 50MP camera? Now the 50MP print will be much larger - about 2x larger. If you compare pixel to pixel, bokeh on the 50MP will be 2x bigger than the bokeh of the 12MP camera!
That sounds stupid... but follow me here ;)
This is exactly what's happening when we enlarge the image from a crop sensor. If we were to print out an 8x10 from a 12MP FF and a 8x10 from a 12MP crop sensor - we would have to enlarge each pixel of the Crop sensor so that they'e the identical size to the FF. And if we enlarge the image - the bokeh blooms will enlarge as well. :)
Bokeh is affected by focus distance, aperture, AND the size of the sensor.
Now to come back to try to explain why two images from the same FF sensor have the same bokeh even though _theoretically_ the higher MP count has a shallower depth of field. I may have been a bit quick to tie resolution to circle of confusion - there is obviously a link. But Circle of Confusion isn't defined by pixel size, it's defined as
CoC (mm) = viewing distance (cm) / desired *final-image* resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25
In the case of Full Frame they use d/1500 (d=diagonal of the lens) as short hand giving us 0.029mm as the CoC. Rough math puts a 12MP pixel at around 0.008mm and 50MP at 0.004mm - both of them are well below the CoC using d/1500 standard.
Using that standard the 12MP and the 50MP FF sensors have identical DoF because both pixels are _smaller_ than the CoC. But if we continue to enlarge the image (the third variable in the CoC equation)- the CoC will get smaller and smaller. It's only when we enlarge the image so much that our CoC is inbetween 0.008mm and 0.004mm that we can start to say that that the 50MP FF sensor is shallower than the 12MP FF sensor. Until then, as long as the CoC is bigger than the pixel size, both cameras have identical Depth of Field.
Your method of teaching is insanely solid John! I think im going to use your stuff to start off some ACs!
Great explanations of very complex subjects. Very well done!
Thank you so much again. Best on TH-cam truly.
This is great! The visuals are a big help (cameraman banging his head on the keyboard was hilarious) Thanks!
Just fantastic video, explaining this whole concept with good examples.
Best explanation for this subject ever!!!👍👍👍
Thank you for these videos! They made me see the process of 'taking a picture' in a whole different perspective. Keep doing these videos! :)
I'm not even involved in filmmaking. I just watch this channel because the videos are extremely well made and entertaining
You are magnificent, I've been so confused about focus vs depth of field for so long
Thanks, John. Brilliant videos.
Great content!! Tnks for all the support for the photography community!!
Nice work!!! The experiments are super interesting and show perfectly what you want to tell!!
Your last point is the best summary. It is not about the sensor size, it is how you shoot.
I bought my 5D mark III because I was used to my 50mm lens being 50mm not 80mm. Although I like using my T3i to get that extra reach with my 300mm zoom lens once and awhile. This is one of my favorite videos you have done John. I understood depth of field from my 35mm photography days. But had trouble understanding it with my APS-C sensor on my T3i. You really brought it to life for me on seeing the difference now and I will be better at using both cameras more creatively now.
great info. best channel on YT. j.
excellent examples and explanations! Congratulations for your work!
Your videos are amazingly interesting. Even the CGI videos which I probably master more than you do are absolutely brillantly explained and accurate. Well done
Thank You, Sir,,, I would say This is one of The most informative and well-presented videos
I have seen...
I'm definitely going to have to watch these videos on lenses and sensors a few times before I fully understand them but these are really helpful. thx.
I Salute you! I honor and respect you and all you have gone through to get you to your levels of intelligence, wisdom and skillfulness in communicating (teaching) so effectively. I am new to photography and self taught. I did not know what I did not know. Inasmuch I remained niggled by a prompt to remove this ignorance of the physics you so eloquently explained / demonstrated. I now know what I do not know. I will avail myself of your body of work. Thank you!!!
Excellent video!Thank you!
Excellent again! Familiar stuff, but great demonstrations! Thank you
Simply perfect lesson! Thank you)
I won't go to film school. I just watch all your videos :)
Spot on facts, simply explained - You, Are, GREAT!!
I wish I had stumpled upon this video (and channel) in 2016. Thank you sir! Very plain language, beautiful demonstrations 😊
Perfect explanation! :)
This was super, thanks John.
Thank so much, this is the best explanation about lens !
John, you are awesome man!!! Thanks very so much for these lectures!
Have just watched 10 seconds and already know it's gonna be something great! ;)
Ironically this is the first tutorial you've ever made which is out of focus. ;-)
+Symon Says TV I noticed that too, glad to know it wasn't just me. I wholeheartedly believe he did it on purpose.
same here, hope this was on purpose.
its the nature of the subject material...circle of confusion
i got many many many thing to learn in this video. it was a full of information and this video clears my lots of confusions. thank you so much sir i just love the way you describe.
Great explanation, those examples really helped!
very nice lesson! Thanks, John.
NIce Shining reference on the sample photo.
Thank you so much for this great video!
This is great! I've been seeking this kind of photography content.
Awesome knowledge! Really helped me a lot.
indeed a wonderful teacher, respect
excellent explanation
somebody give this man a tv show
Another great video! This one had to take a while to make! Thanks!
I know im like 5 years late to the party, but I love how you used the Stephen King theme while explaining.
Thank you so much for making these videos mate. They are incredibly insightful and they make me better at my job ;)
Small correction: You can never get the same field of view by moving the APS-C camera back. You can match the framing on your subject, but the angle (field) of view stays the same so your foreground and background will be different (i.e. the perspective is different). The only way to match field of view is by using the equivalent focal length.
Great work, thanks!
Your practical examples with the magnifying glass are just insane! Thanks a lot for the video, helped my life out, hahahaha
Great explanation
Always informative and entertaining! This is the only channel I watch long videos on YT.
BTW, I still believe Mr. Grady was the real caretaker. :)
+DAVIDSDIEGO He's always been the caretaker..
Thanks! Great explanation!
Another perfect video. Thank you very much indeed.
Excellent explanation.
Best explanation ever!!!
As always! awesome clip - liked
Man, your videos are just awesome! Thanks so much!
Nice video, thanks for sharing!
Bloody awesome series, I hope you're getting some rep out of all this hard work
Finally I came somewhat close to understanding this topic.
It was simply amazing sir.
great video! informative and well explained.
I love your teaching
Thank you for this site, it is great.
John, Once again your wealth of knowledge and the way you breakdown everything is by far one of the best I have ever seen. Thank you so much I love your classes, truely educational. BTW where did you find the cartoon b-roll at 10:44 that is hilarious!!!! LOLz
awesome explanation again like your other videos....
What an excellent and informative video -really well spoken and laid out. I found this interesting and incredibly useful as someone who is moving from using only 120 & 35mm to 4x5 film. Your examples are grounded in digital sensors but everything is totally applicable comparing film formats as well (except for pixels vs grain). Great instruction, thank you for including the math.
I've started to shoot 4x5 and it's so fun but intimidating
@@FilmmakerIQ Yeah I think there are a lot of things that can go wrong! I have ordered an intrepid camera system with all the bells and whistles including the enlarger. I think the key with 4x5 is to plan how you are going to use the camera, write down all the steps and absolutely never rush. I am pretty careful and meticulous, but we will have to see how quickly I make my first mistake and toast some expensive film :)
** also if you are getting into 4x5, I highly recommend looking into Caffenol-C-L development if you haven't already. It's quite a game changer, and now how I exclusively am developing any BW film at home.
Loving that Overlook Hotel carpet!
Another awesome video, thank you!:)
Just amazing content again. Big THX.
Hi John, I love this video, finally someone explained this so clearly and with plenty of evidence. I just wonder if you would expand the topic at the end of the video a bit, which is about different sensor sizes have different looks, I'd love to see if you could make a comparison between the look of different sensor sizes AND analyze them through a scientific way, for example IMAX, Alexa 65, Alexa LF, Super 35, and Super 16 etc.
Love this video. But love that carpet from the Shining the Monkey is sitting on.
Your videos are truely fantastic! Not only can a b*tchslap my fellow photo-nerds with science (lol), I also learn more of the fascinating aspects of my beloved hobby.
Thank you for your great work!
Btw. Nice Shining-carpet ;D
I love these videos.
the ISO crop factor is 1.6*1.6=2.56,
so the iso is not 500*1.6=800, it should 500*2.56=1280
that will give the same look
Can't wait for your paid photo and video courses. This is too good, to be free!
Awesome....like every video!
This single video could create peace on Earth if all photographers watched it. 😁
Love it, another informative awesome video!
I have already praised this video. But I feel I need to again, I just had to share it to a few individuals that were arguing with me on the DOF sensor size issue. Your video explains it really well and helped me make my point perfectly.
+biscuitsalive I was afraid to tackle this subject about a year ago because there was a point in my life where I would have been arguing with you on this matter. I had to make sure I was armed mentally for what this subject meant and how to explain it.
This video has been one of the more controversial ones for sure. Thank you for sharing!!
+Filmmaker IQ it's excellent! I occasionally make camera related videos. And if my videos were half as well thought out and delivered as yours I would be very happy indeed.
+Filmmaker IQ can I get your opinion on something please? It may help settle an argument.
I did a test video a couple of days ago. See "can you spot the camera sensor size from the shot"
On my channel if you have time.
Ok, so the point of contention is- the speedbooster is only changing the FOV allowing me to keep the same distance and framing. (Simulating a wider lens)
(Others were arguing the booster was narrowing the DOF)
But if you actually break it down. The booster is technically widening the "apparent" DOF. Just as it is widening the FOV. ( as the circle of confusion is reduced due to the widened FOV)
The actual DOF of the lens is not changing. As I'm keeping the focal length. The distance. And the aperture the same throughout.
Would you agree with my thinking here?
Hopefully. Have been having a 3 hour argument over it. :D
+biscuitsalive The technical name for a speedbooster is "Telecompressor" You're taking the image circle from the lens and making it smaller.
So let's say you have a spot of light that's slightly larger than the sensor's Circle of Confusion. When we compress the image - we're make that spot of light smaller - therefore what was previously "slightly out of focus" will now be inside the tolerance for focus.
Following that logic - the booster is widening the Depth of Field regardless of what sensor you use.
What might be confusing is people would jump to the idea that a speedboster increases the fstop and therefore reduce the depth of field. The problem though is that ignores the relationship between the focal length and f-stop ratio. A speedbooster shortens the focal length but does not change the diameter of the aperture. So a 1.4x compressor would take a 50mm F4 down to a "real" 35mm F2.8 - it's no longer 50mm so you can't just look at the F4->F2.8 and make that conclusion.
Actually if you look at depth of field charts - the depth of field widens exactly by the power of the compressor.
+Filmmaker IQ great stuff.
It seems I have the physics in my head working roughly ok now. But you explain things better than i can.
(I'm a typical artist, visual based thinking, and can not write down my thoughts as well as I can draw them. :) )
So essentially the speed booster (metabones call it a "focal reducer" ) is widening the FOV, hence shortening the focal length. AND increasing the f stop due to how the maths works out with the new shorter FL.
So in terms of apparent DOF on sensor, these two things cancel each other out don't they?
So the "apparent" DOF we see in the captured the image remains the same.
(As the shorter FL makes the COC smaller, but the new f stop also makes it wider... So the scales are balanced... No increase or decrease to the COC size)
(Note- I realize the DOF of the actual lens does not change.)
In which case the description of what the speed booster does on their site is very misleading, regarding allowing narrower DOF.
Thank you. I'm giving up on the idea of going to film school. Thank you so much.
if i could like this twice i would. brilliant demo, keep up the fantastic work john.
Love science - thanks John!