Originally posted by Na Horuk Ok, put a prime on your K-1, focus and take a photo. Switch to APSC mode, take a photo. Does the APSC photo have wider DoF than the FF photo? No.
Assuming you haven't changed the lens, focal distance, aperture, or print size, viewing distance, etc. the dof will be smaller on the APS-C image than the FF image.
DoF is used to measure the blurriness of the
final image, the thing we are hanging on the wall and looking at. It's not an illusion, it's how DoF is defined and unless we're interested in capturing and looking at the unprocessed data stored in an image file, it's the most sensible view imo.
You're trying to assign DoF to the thing you'd see in the image plane, that's not how the term has been traditionally used as far as I know.