Copidosoma wrote in post #15598402
part of the problem is that you can't really compare FF and APS-c cameras well.
If you are to compare as close to the same as possible you would need to have:
same lens, same distance to subject (which gives you different framing), same pixel density (because of "circle of confusion issues), same aperture, etc. Often what happens is that the FF crowd does the "to get the same framing you have to be close or use a longer lens... thing which makes major changes to the equation.
So, with as much the same as possible i.e. same lens, aperture, pixel density(pixel density, not total MP) distance to subject blah blah blah. And therefore a cropped image from the FF camera to get the framing the same. The DOF would be identical as DOF is a characteristic of the lens, not the sensor.
It's not a matter of "the full frame crowd", it works the same way for everybody.
Of course, if you keep all the variables the same (including viewing a smaller print from a crop camera to keep enlargement the same) then the DOF will stay the same. Nobody that I have seen is disagreeing with that. What people are disagreeing with is the fact that that is the situation in the real world.
In the real world, photographers are going to stand where they need to, and use the focal length they need, according to the FoV that their camera gives them. Have you ever worked out the position that gives you the perspective you want, and the focal length that gives you the framing you want, for your camera, then thought "hmmm, if I was using a camera with a different FoV I would be standing over there, or using a different focal length, so I'll do that instead"? People just don't work that way. You compose your shot by standing where you need to be for your perspective, and choose the focal length to fill the frame with your subject, without a load of wasted space around the edge.
To get the same composition and perspective you have to change the variables. It is true that a FF sensor does not in itself give you shallower D0F, but the need to use a longer lens from the same position (or move closer with the same lens, but that alters the image) will reduce the DOF. Therefore, to capture the image you want, the FF camera will have shallower DoF than a crop camera.
It is correct to say that a FF sensor does not alter DoF. However, it is not correct to say that "using a FF camera, or a crop camera" does not alter DoF, because you have to use them differently, and that difference alters your DoF.