Re: Sunny 16 Rule (digest 1595)

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Bob Howard writes:

>As I said before in this forum..the Sunny 16 Rule is not just some rule
>of thumb that came from somewhere. It was devised by Jack Tupper of the
>Kodak Research Labs (who I served with on ASA committees) from the
>equations of illumination on a film plane, and the constancy of earth
>illumination from the sun. IT IS GOOD ENGOUGH to test light meters. 

So how invariant are sunlight conditions around the globe?  Is a sunny
smoggy noontime in L.A. really photometrically equivalent to noon in, say
the Swiss Alps (and I don't mean in snow)?  What about seasonal variations,
like noon on the summer solstice, vs. noon on the winter solstice at a
fairly high (or low) latitude?  If the inclination of the pole is
sufficient to generate climactic changes, shouldn't it register on a
LIGHT METER?  Remember that the light is passing through significantly
more atmosphere (or significantly less, if you're up at 15,000 feet).
I'll bet your Alpine pictures will be noticably overexposed if you use
the same exposure as for those noontime pix in L.A.

How about after a major volcanic explosion like the one that caused
the "summer that never was"?

It seems to me that sunny-16 is a great APPROXIMATION, and will give
good results under many conditions.  But any engineer knows you use
instruments to measure REALITY as it is affected by local conditions.

When one learns to understand and properly use a meter, you can obtain
a consistency of results that reduces the need for every shot to be
bracketed in order to guarantee one good exposure.  This is a great
help when the subject is dynamic (e.g. sporting events, live shows,
animals) and you only get one chance to get the shot, or its gone.

It doesn't need to be expensive, just accurate.

	-Greg W.


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