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06-24-2008, 04:08 PM   #46
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QuoteOriginally posted by Miserere Quote
Troy, good point. But let's assume Fred has a digital full-frame camera, and that both Fred and Arnie's cameras are 10MP. What then? Or what if Fred is still using film, but Arnie is shooting a prototype APS-C sensor with 21MP (which I believe surpasses the resolution of film)?
Depth of field is independent of sensor resolution, or film grain, or any criteria other than aperture and magnification on the sensor/ film. Note in an earlier post I said similar DOF, presuming same aperture and the subject filling the same % of the frame, not identical. There are other factors that will affect apparent or visual depth of field. Bokeh, for example, will not affect DOF, but it may affect the appearance of out of focus objects enough to give the appearance of a change of DOF. The one stop difference in DOF mentioned in another post amounts to similar, though not identical.

06-24-2008, 04:41 PM   #47
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QuoteOriginally posted by Wheatfield Quote
Depth of field is independent of sensor resolution, or film grain, or any criteria other than aperture and magnification on the sensor/ film. Note in an earlier post I said similar DOF, presuming same aperture and the subject filling the same % of the frame, not identical. There are other factors that will affect apparent or visual depth of field. Bokeh, for example, will not affect DOF, but it may affect the appearance of out of focus objects enough to give the appearance of a change of DOF. The one stop difference in DOF mentioned in another post amounts to similar, though not identical.
That's what I was trying to prove to Troy. DoF is a mathematical value that depends on sensor size, focal length and distance to central point of focus. What should be considered, however, is that the apparent DoF will depend on the visual medium. If you take a high-res pic with a narrow depth of field and display it at 600x400pix, the DoF is going to appear larger because you're losing resolution.
06-24-2008, 09:03 PM   #48
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QuoteOriginally posted by Miserere Quote
That's what I was trying to prove to Troy. DoF is a mathematical value that depends on sensor size, focal length and distance to central point of focus. What should be considered, however, is that the apparent DoF will depend on the visual medium. If you take a high-res pic with a narrow depth of field and display it at 600x400pix, the DoF is going to appear larger because you're losing resolution.
This is largely correct -- apparent depth of field depends on the size of the projected/displayed image and the distance of the viewer. If the 640x400 image on Arnie's monitor is smaller than Fred's 8x12 enlargement, Arnie's image will have greater apparent DOF.

However, apparent DOF does not depend directly on resolution; if Fred makes a modest enlargement of his film negative to obtain an print with the same size as the image on Arnie's monitor, both images will have the same apparent depth of field (unless Arnie is nearsighted and his nose is pressed against the monitor ).

BTW, the 10 megapixel/21 megapixel scenarios proposed earlier are not limited by sensor resolution. Pixel pitch is about 6 microns on a (10 megapixel) K10D, corresponding to a Nyquist resolution limit of 12 microns. Arnie loses some resolution to demosaicing but in any case this system is sufficient to resolve two lines 20 microns apart (the diameter of the proposed circle of confusion).

Everything scales appropriately for Fred's full-frame 10 megapixel sensor (9 micron pixel pitch, 30 micron circle of confusion).
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