Emily hi,
Theory is great, but there is no substitute to a set of tests using your camera and flash.
Simply stand a subject 10ft away from you and and take a number of different exposures (changing the F stops). This will give you are true guide number for your camera/flash and processing.
Once you have worked out your guide number, now using the correct aperture settings start playing around with different shutter/aperture combinations and see how different you image will look.
Have fun!
Sam Stiglec
www. photographyschool-online.com
"Emily L. Ferguson" <elf@cape.com> wrote:
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.
--
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
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