need help calculating aperture with speedlights
I did some test shots with my Metz 44 on manual on my Bessa R4A with Polypanf 50 ISO.
I shot everything at 1/125, at approx 1,2 meters, flash bounced from white ceiling.
I did test shots of a rather dark scene at apertures 2.8, 4, 5.6 and 8 with flash power set at 1, 1/2, 1/8 and 1/16.
Guide number of flash should be 44 at 100 ISO, so that would be 44/1.4=31 at 50 ISO, correct?
If I remember correctly, the correct aperture is guide number divided by distance to subject.
The only good negatives are f/2.8 and 4 at 100% flash power an f/2.8 at 50%, the others are too thin.
But these apertures are much bigger than my simple calculation suggested (i.e. GN31/1.2m = f/25). Where did I go wrong? How do you take into account the bounce flash when calculating aperture?