Chuck Norcutt wrote:
> 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.
When we will see the first OM with "ASA" shutterspeeds of 1/1600 1/800
1/400, 1/320, 1/200, 1/100, 1/64 etc?
Did you ever see an ASA 500 film?
> Fortunately, the ISO rating is based on the old
> ASA standard and not the DIN standard.
So the second number in ISO designations, for example ISO100/21° or
ISO50/18°, is an error?
Just curious.
> The DIN number was "just a
> number". It didn't have a useful meaning like the ASA/ISO value.
"Usefullness" is debateable, but at least, with DIN numbers it´s easy to
calculate in 1/3 stops, because 1 DIN equalls to 1/3 stop.
Regards
Richard
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