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[OM] Re: Coverage angle of T-32, was: Vivitar 550FD M/P/O discussion

Subject: [OM] Re: Coverage angle of T-32, was: Vivitar 550FD M/P/O discussion
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Sat, 08 Jan 2005 18:49:43 -0800
Fernando Gonzalez Gentile wrote:

>Hi Moose
>
>Well I had some time on my hands when I was 25, a white big wall very near
>my house, a new T-32 and a almost new 28/2.8 - unfortunately the 24/2.8 was
>too expensive for me at the time.
>
>I must make some corrections to my former post, now that I've found my notes
>and the slides.
>
>Test was done in two shots on Ektachrome 100 (EN 135-36) on Nov. 1985.
>
>First one says "Zuiko 50mm f 1.4 @ f2.8, Olympus T-32 flash @ GN 32,
>distance 11.45 meters".
>
>Second says "Zuiko 28mm f 2.8 @ maximum aperture, Olympus T-32 flash @ GN
>16, distance 5.71 meters".
> 
>Wide open, the ektachrome 100 came underexposed and with noticeable falloff
>compared to the 50 @ 2.8 at the corresponding distances from the wall.
>
I think you are correct in assuming that there were multiple factors 
compounding. According to Gary's tests, the 50/1.4 should have very 
little falloff at f2.8, while the 28/2.8 gets a 'C' grade wide open.

The overall exposure difference is harder to evaluate. A clue may be in 
your following pp.

>Besides careful distance measuring and outdoor night shooting, now I wonder
>if four AA Ni-Cd were enough to fully charge the condenser despite the
>charge lamp being lit.
>
If reasonably fully charged, the batteries were likely capable of fully 
charging the T32. A question would be whether they wre given time to do 
so. I believe it is generally known that the charge light may light at 
as low as 75% of full capacity on electronic flashes. I'm sure there is 
more precise data in the archives. To do tests like yours, one must wait 
15-20 secs, more if the batteries aren't at peak capacity. past the 
light illuminating to be sure of a full charge. When using the bounce 
grip, the charging rate is fast enough with healthy batteries that the 
time difference isn't as long.

>Now that I've got a PBG2 I know what does a fully charged condenser mean. 
>Anyway, this doesn't explain why the 50 @ 2.8 slides were correctly exposed.
>
It might, if the time from charge light illumination to shot was fairly 
short and was different for the two lenses. Also, if the T32 was really, 
really new, that could have been a factor. The capacitors in new flashes 
aren't fully formed and don't reach their full power until used for a 
while. If you were still in that curve, the power could have been 
different for the 2 shots, especially if that has a differential impact 
on the full and half power setting of the flash. Too many variables!!

Moose





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