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06-18-2013, 01:54 AM   #16
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I just found it neat to be able to blur the sea spray in a pinch without a ND filter at hand.

Diffraction, well yes, but this was a handheld 1/10 sec shot anyway.

Regards,
--Anders.

06-18-2013, 04:27 PM   #17
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QuoteOriginally posted by Cannikin Quote
If you really need that crazy huge DOF, you're probably better off shooting with a wider angle lens and cropping than shooting at f/40. Chances are you'll be losing less real resolution by cropping than you will from diffraction at that small an aperture.
Just curious.. shouldn't that be the same thing? You get the magnification of Airy dics you save using a smaller focal lenght right back when cropping.
Anyways, in ideal world we'd have tilt lenses for this situation . Maybe focus stacking is the more realistic option.
06-18-2013, 04:39 PM   #18
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QuoteOriginally posted by c-meier Quote
Just curious.. shouldn't that be the same thing? You get the magnification of Airy dics you save using a smaller focal lenght right back when cropping.
You're probably correct on that one, well thought about it.
06-18-2013, 08:03 PM   #19
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At 30mm focal length on APS-C and f/40, the hyperfocal is attained at 45.12" with the near focus limit at 23.24"


Steve

06-19-2013, 12:50 AM   #20
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QuoteOriginally posted by c-meier Quote
Just curious.. shouldn't that be the same thing? You get the magnification of Airy dics you save using a smaller focal lenght right back when cropping.
Yes, sorry, you're right. I forgot to account for the crop/magnification factor in the CoC before calculating equivalent DOF (cropping shrinks the apparent DOF, meaning you have to stop down more).

To get equivalent DOF between two lenses of different focal lengths, and cropping the shorter to the same AOV of the longer, you will have to stop the shorter lens down to f/(f-number of the longer/crop factor). So for instance if you have a 60mm lens stopped down to f/40, to get the same DOF on a 4x cropped 15mm, you would need f/10. This is the same absolute aperture diameter, so when the two images are viewed at the same size the effects of diffraction should mathematically be equivalent in terms of optical resolving power (smallest possible detail resolved in terms of angular diameter).

Last edited by Cannikin; 06-19-2013 at 01:20 AM.
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