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Re: [OM] Flash guns for OM4T

Subject: Re: [OM] Flash guns for OM4T
From: HI100@xxxxxxx
Date: Fri, 22 Sep 2000 06:08:36 EDT
 chling@xxxxxxxxxxxx writes:

<<  On the other hand I found using fresh alkaline batteries with
 longer charging time, the power is 0.2-0.3 stops higher than using Ni-cd,
 may be due to higher battery voltage. 
>>
Charles,
        Some flash guns have a voltage control loop so the final flash 
voltage (after some time) is more tightly controlled and largely independent 
of battery condition. The Sunpak handle mount 522/544's are examples. As far 
as I remember the T32 does not use a feedback loop but the BG2 definitely 
does. So if you want more consistent flash output the BG2 should be your 
power source.  The intermittent whine of the BG2 is as a result of the 
control loop stopping and starting the invertor. The control loop in the BG2 
uses a neon tube to start and stop the invertor based on breakdown voltage ( 
a bit primitive). A redundant neon tube is used for safety.  The Sunpaks use 
a zenner diode  detector with a loop filter that causes similar hunting in 
the invertor sound.  The Metz CT45 has no feedback but uses a different 
transformer tap for Alkalines and NiCd's. The battery chamber has an extra 
contact for the rechargeable NiCd pack which is different.

>>
Does anyone have a flash meter want to join the test?
<<

 I posted a very long rant about GN's (with measurements )
a very long time ago to this list so it should be in the archives.

Here are some of those old results repeated:
Measured at 6ft (184cm) with Quantum Calcuflash meter 
                                                          Ratio
            (EV) GNmeas (ft)  GN spec   spec/meas
T20                    8*6  = 48     65         1.35
Viv4600            13*6 = 78    100         1.28
T32                    13*6 = 78    104         1.33
Sun522               13*6 = 78  120?        1.53?
Sun544                7*6 = 102 140         1.34
Sun5000/611     20*6 = 120  160         1.33

So here the specified GN's were reasonably consistently 
1.33 times larger than when actually measured in a dark 
walled, dark ceilinged room, and across 3 different vendor's flashes.

      Tim Hughes
      >>Hi100@xxxxxxx<<


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