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GN Need Help Please to understand Distance Flash to Subject.

billh1401billh1401 Member
edited May 2013 in flash & lighting
I shoot with a Canon T3i, and use Yongnuo YN 565EX ETTL Flash. I am really trying to learn to use Manual Flash to become proficient at portraits inside and outside. The reason I am asking you about this information is because I like your thought process of making things easy with shortcuts. I believe in the old saying KISS (Keep It Simple Stupid). That is what I try to live by with my photography. I would like to be able to keep it simple for my Flash Photography and not be fumbling around wasting time.

My question is this, manual for my Flash says my GN is 58 or am I totally confused. If I am trying to figure out the proper distance of Flash from subject by the Formula of the GN you presented in you book "Off-Camera Flash",
Could I just reverse the formula and do: Distance = GN/Aperture
Exp: (Chart) for a zoom of 35 and a power output of ΒΌ @ ISO of 100
19.5(m)/64(ft) & an f/8 Aperture

64/8 (f/8) = 8ft
Distance = 8 feet


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