zone plate distortions, was RE: Zero pinhole camera

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From: Sam Wang (stwang@mindspring.com)
Date: 05/08/00-09:51:45 PM Z

At 9:22 PM -0400 5/8/00, Judy Seigel wrote:
>
>Actually I was thinking of the zone plate pinhole prints by a onetime
>student of Sam Wang's that I saw in The Pinhole Journal. So either I
>generalized from the particular mistakenly, or what to me looked "soft
>and distorted" wasn't -- or anyway not to someone else !
>
>Judy
>

Sorry, but I was buried under end of semester grading and have not
been able to dive in till now.

Yes, zone plates do distort. For normal focal lengths, no. But once
you use it as wide angle, you will find quite pronounced pincushion
distortion, especially if you use a red filter to sharpen up the
central area of the image.

Moral: don't photograph people's faces near the edges of the frame if
you value their friendships.

BTW, a red filter also shortens the focal length a tad.

Sam Wang

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