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Message: <blockquote data-quote="WayneF" data-source="post: 316629" data-attributes="member: 12496">Rocketman, I obviously owe you an apology, since you did clearly state the flash distance was one meter, and somehow that went right by me.   Somehow I never realized it.  It was my mistake, sorry.   So I think your procedure was great, but the results seem off.If SB-900, ISO 100, full power, FX, 35 mm zoom, the guide number is 34 (meters, manual page F-19), and metered exposure should be f/34 at one meter.Your metered number was more than one stop low?And the SB-700, ISO 100, full power, FX, 35mm zoom, the guide number is 28 (meters, manual page H-23) and metered exposure should be f/28 at one meter.Yongnuo 560 manual (at end) says Guide Number 39, or f/39.Exactly matching the exact number is not a realistic expectation, but it should have been greatly closer.Since all three were off, I'm suspecting the meter, maybe the wrong dome on it, or low batteries, or not metering in center of flash beam, or something?Maybe it was not direct flash?   Bounce could serve as a valid comparison, but the manual Guide Number chart I am trying to use to verify is Direct Flash only.Seems to me a picture (of the meter on its stand) with the camera near the flash position, exposed at the metered fstop, should strongly demonstrate the result accuracy. If the flash were defective, and only feebly trying, still the meter should meter this and the picture should be exposed well.But if the meter was not seeing it right, the picture would not be right.If the manuals guide number chart number were simply used at the appropriate flash distance, the picture ought to be pretty good.  That is the point of it.  GN = Distance x fstop number.</blockquote>

Verification