George S. said to Olaf:
"Sunny 16" just refers to a good starting point to figure an
exposure. Apparently, I assume, this came from the days before there
were
in-camera meters, you had to bring along your meter. If you forgot to
bring
it, you could guesstimate from the sunny 16 rule. You would choose a
shutter
speed equal to the film speed.
F/16 refers to a bright sunny day. You would then open up the lens as
conditions (clouds, overcast sky) dictated. The 1/125 at F/16 is OK if
your
film speed is 100 or 125.
------------------------------------------------------------------------
I'll go just a bit further and assert that this is actually where our
film speed ratings come from. The ISO rating is the inverse of the
correct shutter speed using the "sunny 16" rule. An ISO 400 speed film
will yield correct exposure under bright sun at f/16 with a shutter
speed of 1/400 second. Fortunately, the ISO rating is based on the old
ASA standard and not the DIN standard. The DIN number was "just a
number". It didn't have a useful meaning like the ASA/ISO value. Now
the young whippersnappers will have to ask: "What's DIN?" "What's ASA?"
Chuck Norcutt
Woburn, Massachusetts
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