Originally posted by Rondec The differences with regard to depth of field are primarily noticed on the wide end. There isn't really an APS-C equivalent of something like the FA 31 limited on full frame. That said, I don't really use shallow depth of field with wide angles. For most landscape photographers, the goal is to having things in focus, not blurred out.
Let's say I'm doing a 31 limited on full frame, say, a late sunset. I don't want any noise, so I'm shooting it wide open.
Hyperfocal is 60 something feet. Things are in 'acceptable focus' from 30 feet to infinity.
My friend is using a 21mm f/3.2 on APS-C. Hyperfocal is 24 feet. Everything is in 'acceptable focus' from 12 feet to infinity.
The APS-C/21mm has more things in focus but also has roughly 3 stops worse noise (or slower shutter duration), and only 65% of the sharpness (assuming both lenses are ideal, or at least equivalently flawed).
A lot of the time... maybe even MOST of the time, the landscapes I'm taking a pictures of are WAY past 50 feet away from me. The other times, I can go to F/5 on my FF, still have 1.5x better sharpness and lose nothing in DOF or SNR.