On Sun, Sep 03, 2000 at 02:57:19AM +0800, C.H.Ling wrote:
> Hi Richard,
>
>
> 2. I have not formally test the 180/2.8 at different apertures, since I
> found the problem with my shot at F5.6 so I expected it was not due to wide
> open. And then I made the assumption that "Stop down the lens does not seems
> to improve the situation."
>
> C.H.Ling
>
Cromatic abberation is infuenced by stopping down. I also guessed wrong, when
ased by a lens desiger. But due to cromatic-abberation the colors are focsed
at different distances. This difference stays the same but the circle of
confusion
caused from this difference is reduced when stepping down.
This is the reason why APO is more importend for fast telephoto lenses.
Frieder Faig
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