Chuck,
I've been thinking about this a little bit. (too little as
you'll soon read).
Did you use the meter to trigger the flash? Or did you have the
meter in "capture" mode? When used as the trigger, I believe
you are correct in that the "shutter speed" of the meter was
trimming off the flash exposure. This is not uncommon when using
radio and optical slaved strobes where there is a slight delay
before all of the flashes are triggered. What happens is the
duration of the flash, which is normally within the 1/500 window
is actually skewed and part of the flash dump occurs outside the
1/500 window.
My Poloris flash/ambient meter doesn't seem to be affected by
this as much as I've seen the Minoltas affected. Hmm. I wonder
if the flash meters are getting discontinued????
I asked about 18% vs 13% because the incident domes are
published as 18% equivelent. If this is true and the
manufacturers are utilizing 13% to determine guide number, then
I'm thinking that this would account for the 1/3 stop variance.
Unless my math is wrong and it's actually the other way around.
I revisited this last night and found that my 285HV truely was
putting out the published amount of light. One big problem with
the 285HV, though, is the zoom head does not produce a uniform
pattern of light. To illustrate this, take your flash and A1
out to an empty parking lot at night and fire the flash at full
power with the different zoom positions. Have the A1 on manual
exposure mode and use a much wider zoom position on the lens so
you can see the entire flash pattern.
The 285HV's pattern at 50mm setting can have more than a
half-stop variance across the designated FOV. At the wide
settings, I get over one stop variance. This is why I only use
the flash with diffusers unless I'm shooting over 50 feet away.
As soon as I saw the pattern and falloff I started searching for
an affordable barebulb flash. (still looking).
AG
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