Field of View and Depth of Field

Just mucking about a bit.

First off: field of view. Taken with my D40 (approx 1.5x crop factor) on tripod, so camera is stationary between shots. I know I overuse Mr. Washington here, but he's a nice subject and very patient. My exposures and focus could be more consistent, I wager.

28mm f/2.8 @ f/5.6


50mm f/1.4 @ f/5.6


85mm f/1.8 @ f/5.6


105mm f/2.8 @ f/5.6


200mm f/4 @ f/5.6


So what if you take a wider angle lens and crop? You get the same perspective as a longer lens, but what happens to depth of field?

28mm f/2.8 @ f/5.6 cropped (note we are at like a 200% view -- this lens is sharper than it appears)


50mm f/1.4 @ f/5.6 cropped


85mm f/1.8 @ 5.6 cropped


105mm f/2.8 @ f/5.6 cropped


For reference, here's the 200mm f/4 @ 5.6 again:



So this is a well known phenomenon, but one that still surprises me. The same thing would happen if I compare a 50mm lens on my D40 to a 75mm lens on my full frame FM, shooting from the same position and aperture I would get the same perspective, but the depth of field would be greater for the 50mm lens.

For a much fancier lens simulator, check this out:
Nikon's lens simulator