In article <4cvkqk$2rr@dub-news-svc-5.compuserve.com>, 72774.3546@compuserve.com says...

>I thought that the "charging" that takes place is charging up of a
>capacitor (or similar circuit) in the electronic flash unit. In this
>case, I would assume that the "flash" is powered by the energy stored
>in the capacitor. (Since the relatively low voltage battery cannot
>provide the "kick" required for the high-powered output of the
>"flash", the energy is built up in the capacitor first so that it can
>be released all at once in a shorter amount of time.) The weaker the
>battery, the longer it would take to charge up the capacitor. But
>once the capacitor is -FULLY- charged up, it should contain the same
>amount of energy, whether it took 4 seconds or 60 seconds to -FULLY-
>charge up. So theoretically, assuming the flash output level is
>proportional to the amount of energy powering it, then the flash
>output level should be the same amount each time

x >(given the same lighting conditions being read by the sensor or
x meter).
x This last line is correct if full power is sufficient to cover any
x auto or TTL power requirements for a particular photo, but should
x be separated from the above (about maximum [manual] output being the
x same, regardless of battery condition, so long as the batteries are
x good enough to charge the flash).

This is an interesting point. "Power", though, is current X voltage
(if I remember it right..., and I could easily be wrong in the following, so let's hear from someone who knows more, or who still
has a flash meter and can check the maximum output level from a
flash with fresh alkalines vs. nearly dead ones [with the maximum
charge the set of batteries is capable of]). While a range of battery voltages is sufficient to operate the capacitor charger, I believe
(but I am willing to be converted!) that the total (high) voltage
stored in the capacitor(s) of the flash is proportional to the
voltage of the battery (which is why, if I am right, the maximum
output power of a flash would be less using NiCads and greater using
a hefty gel-cell than alkalines, since the voltage available to the
flash from the batteries would be different). It is possible that,
even with some battery voltage variation, the flash capacitor(s)
get charged to the same voltage. (I shoulda checked this while
I still had my flashmeter, though the sound of the "pop" when the
flash is fired sure is different when using different batteries!)
So, techies out there, who is right???
Hope This Helps