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Old Apr 13, 2005, 5:27 PM   #11
Join Date: Mar 2004
Posts: 39

Try this. It might help.

Mount a 300mm lens on a film slr, set the aperture and frame the picture. Now stand at the same spot, mount the lens still set at 300 on a dslr with a 1.6 crop factor. Try to frame EXACTLY the same picture, but you cannot do it, you cannot get it all in. You have 2 options. Move back with the lens still at 300 until you get EXactly the same picture. Because you are further away, the picture you take will have greater dof than the closer shot taken with the film slr. OR, you can zoom to a shorter focal length to get EXACTLY the same picture as the film slr from the same spot. In this case too, because the focal length is shorter, the dof will again be greater than the picture taken with the film slr.

In short, if EXACTLY the same is picture taken from the same spot with the same aperture, the dslr with a crop factor will have a greater dof than the film camera picture with no crop factor.

If you compare two images of the same subject taken from theSAME vantage point, with the same lens set at theSAME focal length, there will be less subject matter in the picture taken with the lens on a dslr than on a film camera, but the dof of the two images will be identcal.

I too was confused until I worked out this explanation.

But I don't know if it helps.

ken from the uk

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