Nope, mine is only 1000/11. However, it really is about f11. I did some
measurements of mirror lenses and made a long post about them a few
months ago. All that I tested had measured f-stops, adjusted for central
mirror loss, considerably faster than their marked values. My conclusion
was that the makers were marking them with either t-stops or something
that approximated the f-stops of equivalent conventional lenses. Note
Gary's test of the 500/8, where marked and t-stops are very close. Your
new lens may not be as slow as you think!
Moose
Walt Wayman wrote:
I just got a 1200mm f/10 Celestron mirror lens from the critterpix guy.
I'm not sure I'll ever get a decent shot with it, but hey, it'll be fun to
play with. And I got it cheap. I suspect f/10 is a bit optimistic and
that it's probably closer to f/16 in T-stop terms. But that's what they
make ISO 1600 film for, isn't it?
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