00Q said:
Im so confused. Isnt the DoF totally dependent on the aperature of the lens? ie if I use the same lens at the same aperature, I will get the same amout of thing sin focus whether on FF or APSC
Depth of field depends on focal length, aperture, and how close the subject is to the camera.
If you do the following:
(1) take a picture on a full frame at 50mm f/1.4 standing 10m from the subject
(2) take a picture on an APS-C at 50mm f/1.4 standing 10m from the subject
the depth of field is the same, but the field of view will be greater with the full frame. If you crop, you will get the same picture.
But suppose instead, you:
(1) take a picture on a full frame at 80mm f/1.4 standing 10m from the subject
(2) take a picture on an APS-C at 50mm f/1.4 standing 10m from the subject
The field of view is the same (that is, you get "the same picture"), but in the full frame example, the focal length is larger, which means you get shallower depth of field. You could get the same dof by putting 80mm on a crop and shooting at f/1.4, but then you wouldn't have the same picture any more -- the full frame user could switch to a longer focal length (128mm) and get the same picture with shallow depth of field.
