At 03:28 PM 12/10/2001 +0100, Thomas you wrote:
At 21:14 09.12.01, Joel Wilcox wrote:
I hadn't put that together at all. When people say, as I have sometimes
heard, that the 75-150/4 is flare-prone, I guess I should truck out this image.
I'm not sure I understand you correctly here, but remember that flare and
diffraction are two very different lens flaws (diffraction is not a flaw
at all, as there's no way around it).
Yes, my comment was too cryptic. You had said, "Take a look at Gary
Reese's lens tests, and you'll see that as lenses are stopped down their
contrast will suffer. Guess why..." This is because diffraction begins to
play a much larger role in proportion to other factors like the amount of
glass available to resolve the image. I think that would be the answer to
"Guess why"? I was merely jumping to a further thought, which is that my
75-150/4 seemed to be a pretty good performer in giving me the ability to
see the results of diffraction without vitiating them with flare.
I think I now understand why it is important to stop down in order to get a
good diffraction star. One wants to take advantage of the larger role that
diffraction will have on the image. But couldn't this explain differences
between lenses and their ability to make diffraction stars? If one lens is
"poorer" at the smaller stops because of diffraction, mightn't it be
"better" at making diffraction stars?
Thanks,
Joel W.
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