Re: Detecting dust on a DSLR sensor

In article <g45i2h$8on$1@xxxxxxxxxxxxxxxxx>, says...

Or a white sheet of paper that is very very out of focus. This means,
at f/22 or greater, like the lens (preferably a tele) is focused at
infinity and the paper is two inches from the lens. Be sure it comes
out gray, not white.

Just a question or two - why do you need to set the camera to such a
small aperture and why is dust less visible at larger apertures?
--

Alfred Molon
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