Yes, I didn't want to go through that whole business. Suffice it to say
that my measurements of several mirror lenses showed that the marked
f-stops are actually t-stops. Even when I measured and subtracted the
area taken by the secondary mirror, I found the calculated f-stop to be
numerically lower than the one marked on the lens.
See the 500/8 test on Gary's test, "T stop close to f/8 (i.e., excellent
light transmittance)" and the Modern Photo tests on Lee's site
<http://brashear.phys.appstate.edu/lhawkins/photo/mp-cat-tests.txt>
where 'f' or 't' or whatever is measured and reported.
Moose
Terry and Tracey wrote:
Here is the difference between f stops and t stops. Basically, the f stop is
the mathenatical rating, whilst t stop is the actual rating. A 100mm lnes at
f4 will let through more light than a zoom at 100mm at f4 due to the
internal elements.
The front element of the Zuiko 500mm must be at least 500/8mm, or 62.5 mm.
How much actual light actually makes it through to the camera is the t stop.
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