11-21-2011, 12:39 AM
Airy disks describe something that exists. Diffraction exists too. CoC does not. It is just a value to make calculations make sense, and how CoC is determined depends on the situation, or what you are trying to determine.
In the case of DOF on APS-C and FF with equivalent lenses (and then of course we are NOT talking about different print sizes, nor different or even defined view size, let alone pixel pitch), only the crop factor to determine the equivalent lenses is of influence.
You can assume whatever sensor resolutions, it is not important here. So leave it out of the discussion... That is just muddying it. Sensor resolution/pixel pitch only comes into play to determine how big one can print with a certain viewing distance in mind.
In the case of DOF on APS-C and FF with equivalent lenses (and then of course we are NOT talking about different print sizes, nor different or even defined view size, let alone pixel pitch), only the crop factor to determine the equivalent lenses is of influence.
You can assume whatever sensor resolutions, it is not important here. So leave it out of the discussion... That is just muddying it. Sensor resolution/pixel pitch only comes into play to determine how big one can print with a certain viewing distance in mind.