So a crop camera has wider depth of field?
Depends how you look at it. The way I look at it: “only because you will use it differently. If you use it to take the same picture, you’ll get the same depth of field”. But of course for that “same picture” you’ll need a different lens.
OK, this is complicated. So let me just show you by example.
Picture one: full frame 1Ds MkIII camera, 50mm lens at f/1.4.
(You can click to see the large version).
Picture two: crop camera, a Canon 7D, with a 35mm lens also set to f/1.4. That 35mm lens on a crop camera is about the same as a 50mm lens on a full frame camera; i.e. enables me to be at the same point and yet get roughly the same picture. Now I see this:
As you see, this gives you roughly the same depth of field. If there is any difference, it is minor. SO:
A 35mm lens on a crop camera gives you roughly the same picture as a 50mm lens on a full frame camera, and roughly the same depth of field.
A few notes, by the way:
- These results are consistent; not just “one randomly picked picture”.
- The DOF (depth of field, i.e. how much is sharp) is extremely narrow. Great care is needed when shooting at f/1.4!.
- I was aiming a single focus spot at the dot (near the 10) in all pictures (On the 7D, I was using the extra small focus spot).
- I have noticed that the Canon cameras (or is it the lenses?) focus too closely (they “front-focus”) when open at f/1.4. By f/2.8, this effect is either gone or too small to see clearly. In the last picture, I added an adjustment of +15. This does not change the depth of field; it is just to make both pictures about the same.
Point 2 explains a few things to me, by the way. That’s part of the Canon-effect, more on which in the next few days; it’s why I have to adjust extra when wide open.
