Recently I was photographing detail on a tree trunk on 5x4 with a 150 mm lens.
Predictably, close in, depth of field was very small. I had thought that increasing the distance of object to lens, moving the camera back and using a longer focal length, might give me extra depth of field whilst framing the composition as before. Checking depth of field tables reveals the same depth of field in both scenarios i.e. the gain in depth of field from doubling object distance is negated by the smaller depth of field of a lens of twice the focal length.
So it seems the only way to achieve greater depth of field is by a shorter lens or by moving the camera further away, and in both cases cropping to arrive at the same composition. But does not cropping result in a smaller perceived depth of field?
Grateful for any comments.