I'm sure that what you say is true and much of it you've said here
before. But I'm only evaluating the manufacturer's claims which don't
hold much water. And while I say that the T32 doesn't cover a 24mm
lens' field of view very uniformly I would never actually try to take a
flash photo with a 24mm lens with only a single, direct flash... even if
the flash did live up to its claims... not only would the illumination
be uneven but 24mm does funny things to the shape of people at the edge
of the field. :-) As to recycle times, even though I own a BG2 I've
never used it as anything but a handle. I've never put C batteries into
it. If recycle time is important I use a high voltage power supply
which will recycle in about 1-1/2 seconds. Actually, more like 3
seconds since, when used with T32s, I usually have two of them attached
via a Y power cable.
Dr. Flash
Tim Hughes wrote:
> This is hoary old subject related to not only the test conditions
> used for the GN rating, (they assume a smallish room with reflective
> walls) but also if you are foolishly(?) wanting to cover a wide angle
> uniformly onto *a flat surface*. (This is what people are doing when
> they try to test their flash by photographing a blank wall say) There
> is then an inherent power law that varies as something like cos^3
> that is very,very punitive as you go wider. In some ways it does not
> make a lot of sense to try to cover a flat surface uniformly either,
> when using a direct on flash small reflector, as this would require
> very nonuniform high power/steradian at edges, blowing out near
> objects at edges of frame. You are better off doing room or ceiling
> bounce or using a large area flash diffuser like a beauty dish, light
> box, umbrella etc. to reduce cos^3 law effects.
>
>> like the others they also fudge on the recycle time claiming 10
>> seconds from a full dump. At 10 seconds the flash is still 1/3
>> stop away from max power and it's still 1/10 of a stop away after
>> 20 seconds.
>
> Actually this varies a lot by vendor. In the Case of T32 that is true
> off the internal batteries , however T32b is much more consistent if
> used off of the bounce grip 2. This is not just battery size, the
> reason is the bounce grip uses voltage feedback control of the output
> capacitor voltage, making flash power much,much more consistent, even
> when the batteries wear down. Also the BG starts chirping when it
> reaches correct voltage, so even when batteries get older you still
> know how long to wait to reach full charge. Using a flashmeter with
> the T32 on its own, still puts you somewhat at vagaries of how long
> you leave T32 to charge again, after the test flash. Even old handle
> mount flashes like Metz 45/60 etc or Sunpak 522,544 555 etc regulate
> the voltage to the capacitor using feedback control, so these again
> charge faster (esp 6 cell units) and work more consistently. Most of
> them also change their chirp to an intermittent pulsing (like
> BG2)once they reach full charge, giving nice audible feedback as to
> when they are fully ready/reached full voltage.
>
> Most modern flashes even smaller units, use voltage feedback control,
> not only for flash consistency but for power saving, since the
> inverter is cut off at full voltage and only cycles on periodically,
> for top up (so chirping). I have a Nissen flash unit that eventually
> goes into a power save mode that stops cycling the inverter after it
> has sat idle for a very long time. You then touch the on/off switch
> to put it back into the cycling mode to top up. The unit's self
> discharge rate is very low so it stays well charged for a very long
> time even after it goes into the sleep mode. A rather nice feature.
>
> Tim Hughes
>
>
>
> --- On Sat, 11/8/08, usher99@xxxxxxx <usher99@xxxxxxx> wrote:
>
>> From: usher99@xxxxxxx <usher99@xxxxxxx> Subject: [OM] Re: News
>> "Flash" To: olympus@xxxxxxxxxx Date: Saturday, November 8, 2008,
>> 8:20 PM More sound advice from Dr. Flash. Thanks, Mike
>>
>>
>> Just a different way to fudge the numbers. Some won't notice that
>> the spec is at ISO 200 rather than 100 and most won't know how to
>> do the numbers to convert 160 at 200 to 113 at 100. But that's an
>> easier conversion than trying to compare the T32's guide number of
>> 104 at 24mm coverage angle to someone else's guide number given at
>> 105mm coverage angle. It's especially difficult because Olympus
>> also fudges the 24mm coverage number... it's really more like 28mm
>> as there is already 1/2 stop falloff at the edge of the field of a
>> 28mm lens. They also just plain lie about the guide number. I've
>> measured 4 T32s (all within 1/3 stop of each other) and they
>> average a guide number of 84. And, just like the others they also
>> fudge on the recycle time claiming 10 seconds from a full dump. At
>> 10 seconds the flash is still 1/3 stop away from max power and it's
>> still 1/10 of a stop away after 20 seconds. Never believe a flash
>> manufacturer's specs and always use a meter.
>>
>> Dr. Flash
>>
>>
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