Walt Wayman wrote:
>Guess what! I quit after the sixth or seventh lens, having failed to discover
>any discrepancy greater than 0.2 of a stop between the marked f-stop and the
>measured T-stop. Hardly worth bothering to note.
>
Back before lens coating, it was a BIG deal. You really couldn't go over
about 4 air-glass interfaces without losing a lot of light. If you look
at old multi element designs, you will see how they maximized glass to
glass and minimized air to glass transitions. I suspect this is where
the specs of both number of elements and number of groups in lenses came
from, 'cause then it really meant something. With the advent of single
coating, it became less of a deal, but still significant with complex,
multi element designs like zooms and fast wides, esp. retrofocus designs
for SLRs. With MC, the loss at each surface is so low that you should
get the kind of results you got with those relatively simple lens
designs. If you look at when various lenses were introduced, you will
notice that faster, wider lenses and longer ratio zooms suddenly started
popping up like mushrooms after a rain when MC became common.
Moose
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