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06-19-2012, 11:08 AM   #1
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when does diffraction start on 645D sensor?

i can't tell when diffraction starts on my 645D.. any real world tests out there or user experience? i've been shooting with my 45-85 lens and f13 looks really good.. f16 and f22 seems a little softer but i'm not sure cause the difference is so subtle..

06-19-2012, 11:27 AM   #2
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Diffraction does not start suddenly at any given f stop. It is a gradual thing. I feel that aberrations and diffraction as causes of unsharpness are aspects of optics that we have to live with as photographers. Trying to shoot at apertures that avoid both, limits our ability to be creative. I use f/45 and f/32 on occasion, knowing full well that diffraction will affect the shot but the composition would suffer if shot at f/11. Getting the shot I want trumps diffraction worries.
06-19-2012, 11:30 AM   #3
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Without looking up some numbers and the formula to do the accurate math I would think f16 should be fine but it should be setting in at f22. on 645 film it sets in above f22 (so f32) but the sensor is smaller than film so i am making a lazy educated guess

and a big plus 1 to the comment above
06-19-2012, 11:53 AM   #4
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QuoteOriginally posted by eddie1960 Quote
Without looking up some numbers and the formula to do the accurate math I would think f16 should be fine but it should be setting in at f22. on 645 film it sets in above f22 (so f32) but the sensor is smaller than film so i am making a lazy educated guess

and a big plus 1 to the comment above
yes that makes alot of sense..

06-19-2012, 05:33 PM   #5
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If you run the calculators on the Clarkvision website and CambridgeinColor websites, you'll see that for a pixel pitch of 6 um (or 8 um depending on which reference you read) the diffraction effects will show up at f16.

Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks
Clarkvision: Digital Camera Sensor Performance Summary
06-19-2012, 05:44 PM   #6
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Format size is the real indicator to the permissible level of diffraction, not pixel pitch. This is always considered when designing lenses. You will notice that the D FA 55mm stops down to f/22. I have no problem shooting my 645D at f/16 and will shoot at f/22 as well. I routinely print 30" or larger. The fact that you cannot really decide whether diffraction makes a significant impact to your image suggests it doesn't.
06-19-2012, 06:37 PM   #7
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QuoteOriginally posted by smigol Quote
If you run the calculators on the Clarkvision website and CambridgeinColor websites, you'll see that for a pixel pitch of 6 um (or 8 um depending on which reference you read) the diffraction effects will show up at f16.

Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks
Clarkvision: Digital Camera Sensor Performance Summary

thank you for the info/links.. really helpful.
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