FX Cam, DX crop mode questions

Started Jan 18, 2013 | Questions thread
Leonard Shepherd
Veteran MemberPosts: 7,927Gear list
Re: FX Cam, DX crop mode questions
In reply to inferno10, Jan 18, 2013

inferno10 wrote:.

DoF does not change when you enlarge an image in post. DoF is determined by your aperture and distances between subject, background, and camera.

(snipped) but your actual depth of field will not have changed. If you compare an enlarged version of the FX shot to that DX shot taken from the same position, you should find no difference in DoF or FoV.

Your first comment might to be misunderstood.

If you enlarge  and increase viewing distance in proportion to the enlargement depth of field does not change.

Is when you enlarge you crop the image you change the circle of confusion and reduce the depth of field.

Your second comment is not accurate.

DX has a smaller circle confusion than FX. Although it might sound counterintuitive the smaller circle of confusion results in a one stop DX gain in depth of field in your example.

Simplifying the mathematical calculation the FX enlargement looses two stops depth of field. The DX enlargement taken in isolation also looses two stops depth of field, but the smaller starting point DX circle of confusion gains one stop depth of field, leaving a net difference of one stop compared to two stops with FX.

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Leonard Shepherd
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