Focusing on Depth of Field and Lens Equivalents

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:

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*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.

[TutorialsJunction]

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 :)

[TonyAndChelsea]

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.

[sottozen]

This is one of those videos i regularly come back to watch...

[Luciusse]

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.

[ShaunakDe]

This is seriously the best video on DOF and sensor size in the world.

[WilliamParmley]

Thank you! After all these years... I never realized that crop factor effects *everything*, not just "equivalent" focal length.

[nobnobnobnob]

Finally somebody who knows and explains the subject very well not is not from the manufacturer side(who wants to market us).

[SchardtCinematic]

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.

[BasicFilmmaker]

As usual, fantastic stuff. Personally, I love the in-depth coverage - sent many a person over here when they have questions. Thank you.

[GiuseppePipia]

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!!!!

[sparkybluefox]

"I can see clearly now" Thank you Mr Hess for this sweet video! I love the work done on this channel!

[WilsonWongWilzWorkz]

Your last point is the best summary. It is not about the sensor size, it is how you shoot.

[bg]

Brilliant! Kubrick would be proud. He was obsessed with tack sharp images.

[allissondiego]

I'm not even involved in filmmaking. I just watch this channel because the videos are extremely well made and entertaining

[jjcale]

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!

[ingridfong-daley]

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

[victorbart]

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 :)

[AGCipher]

Your videos are amazing and every photographer should watch them!! Wonderful explanation!! :)

[chochmah]

I'm so happy every time you upload a video that I thumbs up it within the first couple of seconds.

[LiaoK]

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.