My tests were conducted indoors within a modest size room with white
walls and ceiling and with the diffuser extended on my Sekonic L-358
flash meter. The diffuser extension should allow catching some
reflections. The tests were also repeated with the flash facing in the
opposite direction into another room with no significant differences. I
also waited at least 15 seconds between each shot (sometimes much
longer) and used fresh alkaline batteries. The tests were repeated many
times and results not accepted unless within 0.1 stop of each other.
The flashes were fired numerous times since they were being tested in
all manual and automatic ranges.
I'm confident of the numbers.
Chuck Norcutt
Andreas Pirner wrote:
> Chuck Norcutt wrote:
>
>>Anybody here ever measure the actual output of a Vivitar 285HV?
>
>
>>Measuring at exactly 10 feet one gives me f/8 and the other f/9 or guide
>>numbers of 80 and 90. Since that's about 1/3 stop difference I figure
>>that's probably within the manufacturing tolerances between flashes.
>>But they should be measuring f/12 and that's a stop or more difference.
>>In other words, only half the power that they're supposed to be
>>putting out.
>
>
> AFAIK all flash output should be measured in a
> defined REFLECTIVE location, sort of simulated
> indoors situation. The reflections are expected
> to add to total illumination.
>
> That explains why flash outdoors seems so grossly
> off to the low side.
>
> Then the capacitor(s) need formation once in a
> while. That is to go through several load/discharge
> circles to put them to full capacity again. I guess
> that has taken place with Chuck's tests.
>
> Then the ready lights go on at approx. 70% charge
> and that is official, 'allowed' by some DIN (or
> similar) normation. And all makers do use this
> allowance to 'speed up' recycling times. If used
> in some auto mode, with no need to near full
> discharge, no one ever notices.
>
>
>
>>When I've measured my T-32's and Sunpaks they've always shown to be bit
>>optimistic relative to the spec but nothing like 1 stop below what it's
>>supposed to be.
>
>
> Some maker are more true to reality than others.
> Olympus always was pretty correct with coverage and
> output values, at least with QA and T series flashes.
>
>
>>So, my question is, has anybody else actually measured a 285HV?
>
>
> Not yet ... sorry. I should do, I really should.
>
> Andreas
>
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