YN-622C Q&A

I was checking 550EX and menu control, and one aspect puzzled me. So I swapped to a 580EXII, and found the same puzzle. I have tested several setups, including FEC +-, and the problem remains.

50D + 580EXII. Camera menus checked - ETTL, first curtain, M 24mm zoom, wireless disabled. These two are FEC 0.

Doh! Obvious now - I failed to place the o/c flash in the same head position as the on-camera shot. The shots are now almost identical exposures. It's a sideways shift of 18", but ETTL makes such a different evaluation.

How about change "ETTL II meter ." to average? It's quite different from evaluating. The latter meters the exposure mainly for the subject. So the angle of flashes is very important. Or you may add a third flash as group c for the background.