In a message dated 3/14/01 6:02:59 PM Pacific Standard Time, WKato@xxxxxxx
writes:
<< There are a couple of factors at play here. One as Mike has pointed out is
the secondary mirror, which takes light out because it physically blocks the
light path. Then there is "silvering" which is hopefully silvering rather
than aluminizing. There are transmission differences between the two types of
coating. Then there is aging, where the mirror coating is less efficient.
Often mirror lens are discussed in terms of "T" stop which is a better
indicator of light transmission rather than "F" stop.
PS. I still love mine. Sharp, compact, and goes in my fanny pack. >>
Yes-I have heard of the secondary light loss.
Now here is a neat thing. According to Gandy's awesome site on cameras and
lenses, my Viv Ser 1 450 mirror is Aspherical! Wow! Got to be the only one
made?
I also don't see the donuts so easily, it acts less mirror-like.
John Raymond
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