OK. Flash has guide number of 120. Have no flash meter.
If distance from object to flash is 10 feet and guide number is 120,
at 100ISO the optimal aperture is around f11.
If distance form object to flash is 5 feet and guide number is 120,
at 100 ISO the optimal aperture is around f16.
If diffuser cuts out one stop, aperture at 5 feet returns to f11 - right?
If film speed goes up to 200ISO aperture goes to f16 - right?
thanks.
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Emily L. Ferguson
mailto:elf@cape.com
508-563-6822
New England landscapes, wooden boats and races, press photography
http://www.vsu.cape.com/~elf
