Blog / Crop vs. fullframe given standard prime lenses
Since 50 mm is a universal prime lens in 35 mm format photography, many photographers choose 35 mm prime as a standard lens for cameras with cropped sensors. Can these two setups really be considered equal?
The angle coverage is nearly the same (not exactly because 35 mm focal length for cropped sensor gives a little more than 50 mm), but what about depth of field?
I’ve played with LensTutorial entering Nikon D300 (cropped) vs. Nikon D700 (full frame) cameras to see what it is like. You can easily repeat the same experiment for Canon or other brands using setup menu for choosing right models and makers.
Distance: 1 meter (3.3 ft)
DOF for Nikon D700 with 50 mm: 9.3 cm (3.68 inches).
DOF for Nikon D300 with 35 mm: 12.7 cm (5.0 inches).
Now having the facts lets analyze them:
- Given roughly the same angle of view, these two setups have different DOF: Full-frame camera DOF is more shallow.
- If you’re switching to a full-frame camera from a cropped format note that you will have to use smaller apertures to achieve the same DOF.
- E.g. for D700/50mm lens at 3.3 ft you need to go to f/5.6 from f/4.0 (which is 1 stop EV) to get the same DOF as with D300/35mm lens setup.
- Using smaller DOF in this case can make you use higher ISO or lower shutter speeds to get the same exposition.
- This means that some of the full-frame sensor low-light capabilities are offset by the need to use smaller apertures to get the same DOF as with cropped sensor.