How to determine diffraction limit for a lens?

Started Jun 28, 2011 | Discussions thread
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Don Strimbu
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How to determine diffraction limit for a lens?
Jun 28, 2011

I've been shooting a lot of macro subjects (yeah, flowers again) with my SD15, the 70mm f2.8 DG Macro and the 105mm f2.8 DG Macro.

I read an article about diffraction effects at small apertures, and I understand the concepts of the Airy disk and a sensor's "circle of confusion". That being said, other than shooting test charts, is there a practical method to determine the smallest aperture to use with these lenses to balance DOF and sharpness?

I've generally limit my minimum aperture to f11, just because... is there a method to this madness, or am I throwing DOF away?

-Don

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Don Strimbu | Chicago, IL USA
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