Re: PHOTO-3D digest 1356

[P3D Bob Howard <bobh@xxxxxxxxxxxxxxxxxxxx>]

RE: Exposure and Lightmeters..Greg and Dr. T.

If this keeps up I will have to bring up the wonderful Sunny16 rule 
invented by Jack Tucker of Kodak Research Labs, but named that by the 
photo press. It (shoot shutter set at film speed with f/16 in full sun 
at your back) gives perfect exposures if you learn the offsets which 
correspond to those in the old Kodak guides. e.g. beach, sunny, sunny 
bright, cloudy, dull, shade etc. The reason it works (much like an 
incident light meter) is that the sun gives almost constant illumination 
of the earth if unobscured and when well up (10am to 3pm??). Differences 
can be figured easily. I use the Sunny16 rule to test meters to see if 
they are any good. (a modern matrix metering system built in cameras 
does not act as just a meter but is a look up table based on several 
scene areas sampled for position and intensity!, so cannot be used to 
compare with ordinary meters.)
The inexpensive flash meter is called a guide number!!! Most flashes 
have a calculator you set film speed into and distance and can read an 
f/stop. The f/stop for 10 feet (times 10) gives you a guide number you 
can use if the calcuator isn't handy. The BEST guide number is one 
obtained by trial from test exposure taken at 10 feet flash distance 
with the f/stop recorded. That can be used for other distances later.
BobH


------------------------------