You could put 100 large dust specs inside the lens and never notice the
effect on image quality. Dust has two effects on the image.
1) Dust blocks light. But think how much dust would be required to
block any significant amount of light. Case closed.
2) Dust causes diffraction, diffraction reduces contrast. But every
edge in the optical path also causes diffraction. The edges of the lens
cells cause diffraction. The edges of the diaphragm cause diffraction.
When you've got enough dust specs in the lens to equal all the other
diffracting edges inside the lens you might want to start worrying about
a detectable effect on contrast. Case closed.
Chuck Norcutt
John Morton wrote:
>
> Having had a really good look at the lens in question, I can see no
> sign of the hazing being refered to here; but I do notice a few
> uncomfortably large dust specks internal to the lens that I hadn't
> realized were there. Hopefully, they won't affect image quality.
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