Depth of Field Repealed

SAMCINE David Samuelson & Bill Pollard DoF Calculator

On page 49 of Film and Digital Times February 2018 Edition #86, I wrote, “The difference in depth of field between Large Format and S35, comparing lenses with the same angle of view, is the equivalent of about 2 stops.”

This unleashed a deluge of debate among PhDs, Professors and Lens Designers sprinkled with some solid real-life testing. Is Circle of Confusion still valid? Consensus is not clear.

Uh-oh. It seems that the depth of field could be anywhere from ½ to 1 to 2 stops. So, please do your own tests. And let us know your results.

I’m getting different results when using the same series of lenses on cameras that have the same pixel pitch, like Alexa LF and Alexa SXT (8.25 microns). And something altogether different with different cameras.

And what happens when using 8K cameras with the same resolution: RED MONSTRO 8k VV and RED HELIUM 8K S35? Same resolution, different pixel sizes.

Please post your comments and results.

The lens designers are working on this and will also let us know.

Stay tuned.


The venerable Guild Kelly Calculators showing different DoF for the same focal length in 16mm and 35mm.




Leave a Comment

2 Responses:

  1. Asif Limbada says:

    This was the exact question on my mind too. Also would love to see a clinical test with the following combinations:


    Things are definitely getting expensively interesting.

  2. Angelo Sartore says:

    As a 1st AC, the notion of ‘Depth of Field’ has been rather invalid in real life working conditions for some time. The SamCine & Kelly DOF calculators are not really useful at all anymore as the accuracy is not available on them. With many DP’s wanting to shoot wide open regardless of environment, the question of depth of field is sometimes asked, but rarely answered with any satisfaction. Directors will occasionally ask “can I keep both actors sharp?”. The lens focal length, focus distance & stop will determine that and for the majority of the time, if the actors are not on the same focus plane, the answer is NO! Put large format cameras in the mix and the DOF dilemma increases. Even some TVC’s I have worked on, some pack shots have had an ‘uncomfortable’ lack of depth, where the entire plate of food is not all sharp, or the entire name of the product is not all pin sharp. Artistic or technical decisions discussed & argued beyond my pay grade. I have not bothered to look at a DOF calculator for many years. That’s not to say that I am so experienced, I don’t need to, but it’s futile & sometimes depressing to try & calculate how little depth there is & show you how difficult the shot is going to be to achieve. These days remote focus, cinetape or similar & HD monitoring is standard ( HD monitoring VITAL) & the 1st AC can usually see the focus drop off (then burst into tears). With the speed at which the film set moves these days, I rarely bother with a tape measure, as there is no time. Lasers distance meters are common & very useful, very accurate – and quick. Just my 2 cents worth!

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