Hi Bob:
The Sunny-16 rule came about long and long ago, before the
manufactures removed the the safety factor of about one stop
that they used in rating the films. That is, film went from
200ASA to 400ASA without any change in the emulsion. This
happened back in the late fifties. For best results you need
to put that one stop back into the film rating. Thus you
need to use 1/2 the ASA, or Sunny-11 to get the same results
as you did back then.
If you look in something like the film guide book Focal
Press publishes, you will note most negative films have a
one stop underexposure rating and a two stop overexposure
rating. Using the sunny 16 rule your are several times more
likely to underexpose than over expose. Also the brightest
sunlight is seldom more than one stop brighter than the
Sunny 16 predicts, so you only get -in the worst case- one
stop overexposure, but can get several stops underexposure
using the Sunny-16 rule.
That said many modern color negative films have a very wide
exposure latitude so can take several stops overexposure,
but most only take one or two stops of underexposure so it
may be better to shift the exposure a couple of stops with
film like Kodak MAX. That is, rate it at 200 instead or 800.
These changes did not apply to slide film because it did not
have the latitude to allow it, so the Sunny-16 rule still
applies to it. Though in truth I have underexposed more
slides than I have overexposed, so I tend to use Sunny-11
there also. But, I usually use an incident meter and that is
far more accurate than any rule of thumb.
In the case of the original poster, he should check and see
if his problem is not the lab rather than exposure before he
does anything else.
--Tom
Bob Walkden wrote:
>
> Hi Norm,
>
> if they did then they were wrong (or at least, nobody's told me about
> the change). I can't imagine how film emulsions on their own would
> affect this. You'd also have to recalibrate all meters. It may be that
> you're getting confused with the fact that meters are calibrated on
> 18% grey because early measurements supported the idea that average
> reflexivity in mid latitudes was 18% at midday in midsummer. However,
> more recent measurements claim that the average is 13%. Nevertheless,
> it doesn't seem to make any difference to any pictures, so there seems
> no reason to change anything.
-
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