Roger Scully wrote
> If the coating really makes a
> difference, it is only in a very limited way and probably only if the
> photographer does not properly shield the lens from direct sunlight.
It does make a difference, and here's why. I'll start with some figures
from Robert Monaghan's web site http://www.smu.edu/~rmonagha/mf.
He has a table
uncoated SC MC
glass-air surface 93
% 99.8%
50 1.4 7 elt 41.8
% 97.6%
14 elt zoom 17.5
% 95.3%
I don't know how he arrived at these figures, but suppose for
the moment that each element has the equivalent of 1 air-glass
surface and you get:
7 elt 60.2
% 98.6%
14 elt 36.2
% 97.2%
e.g. for 7 elt MC case transmission = 100 * (0.998 **7).
What matters here is not the transmitted light but the light that is
*not* passed, because most of that becomes flare. So a seemingly small
difference of 99.8% v. 98.3% translates to a big difference of 1.4% v.
11.3% with a 7 elt lens, through the magic of exponentiation. This is
why multicoating reduces flare on lenses and why it isn't as important
for filters.
The other thing to take away from this example is that primes
are better than zooms and slower primes with fewer elements are
better that faster primes with more elements.
If you prefer experiment to theory, all I can offer is that when
I shoot into the sun over water late on a summer afternoon the
50 1/8 SC is unacceptable, the 35-70 Zuiko f/4 better, and
the MC Zuiko primes excellent. I shoot this way quite often.
I don't have a lens hood for my 24 f/2.8 - would the Oly one
vignette with a polarizer behind it anyway? - so I use my fake
Akubra (hat) to shade it.
Note that sometimes flare just manifests itself as overall reduced
contrast, which you might not notice if printing to B & W. With
colour slides you can get ghastly colour casts bled from
sections of the image.
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