[pentax_amateur]

The focusing issues during video recording (using KP in my case) prompt one to use an f-stop with a great DOF. However, DOF for video is probably drastically different from that for stills, since video "resolution" is much lower than photo resolution. When plugging numbers into a DOF calculator, we should probably use a different Circle of Confusion for video. Any idea what it should be? Should one just increase CoC three-fold (6000/1920=3), or is it more involved?

Somewhat related: what DOF calculator are you using? The android DOF calculator that I like does not allow me to select a specific sensor size, but rather lists "Pentax DSLR". I suspect not all "Pentax DSLRs" have the same sensor.

[PiDicus Rex]

The focusing issues during video recording (using KP in my case) prompt one to use an f-stop with a great DOF. However, DOF for video is probably drastically different from that for stills, since video "resolution" is much lower than photo resolution. When plugging numbers into a DOF calculator, we should probably use a different Circle of Confusion for video. Any idea what it should be? Should one just increase CoC three-fold (6000/1920=3), or is it more involved?

Somewhat related: what DOF calculator are you using? The android DOF calculator that I like does not allow me to select a specific sensor size, but rather lists "Pentax DSLR". I suspect not all "Pentax DSLRs" have the same sensor.

So much 'nope'.

DoF is not reflected in the Resolution. It's factors are the Lens Field of View, Iris opening for that FoV, and the Size of the Image Circle projected by the lens, and size of the sensor (or film) being used.

So, two cameras, one Full Frame, one Micro 4/3rds, can have Identical image resolution, say HD or 4K, but have completely different DoF, for the same Iris and FoV.

And so, DoF for Stills and Video on the same camera, Are The Same, and You should use the same DoF calculation.

NOTE;some bodies will crop more in video mode - K-01 thru KP APSc will have about a 1.65 crop in video compared to stills having full APSc of 1.5 crop factor. The new K-3iii crops closer to 1.8 in video mode. Yes, this confuses the issue, but on the same body with no difference in software cropping between modes, the math is the same for stills and video.

When the camera has different crop settings between modes, that's when the math is different.


Circle of Confusion, in film era, was the smallest item that could be reproduced on the film stock. Now in the Digital Era, it is a combination of the Lens and Sensor, with many lenses now being able to project details on the sensor that are narrower then an individual pixel, and so blurring or shifting to moire as the camera moves or focus changes.


As for the DoF calculator - the better ones will allow you to manually set the sensor size, or you can use a different camera preset to get close enough.