"Gary Morrison" <mr88cet@austin.rr.com> wrote in message
news:3F3AF16A.AC6F3B54@austin.rr.com...
> On my Nikon D100, and I suspect this applies to at least some Nikon film
> cameras as well, the built-in flash performs a virtually imperceptably
fast
> series of preflashes in order to gauge how brightly to fire the flash.  I
> confess that I didn't quite completely follow all of the description in
the
> book, in part because it references single-letter lens types I'm not
> immediately familiar with, but I'm wondering one thing:  can this feature
> be disabled entirely?
>
> I ask because my brother, a freelance photographer, has a "classic"
> portrait-oriented, optically-fired slave flash unit, and the preflashes
> appear to be firing off that unit prematurely.
>
> This gismology is, although very welcome, still a little foreign to me.
> Until I got the D100 a couple weeks ago, the only SLR I've really worked
> with had been with an aaaaaaaancient purely-mechanical Pentax, back from
> the Pentax line's earliest times in America when Honeywell was importing
> them and stamping their name on them.
>

I had a Canon EOS 300 which would fire a series of short flash blasts if
flash was required, it was linked to the auto focus mechanism, to enable it
to operate in low light situations, it also used it as a red-eye reduction
feature, apparently to narrow the pupil of the "victim" shortly before the
"real " flash fired, there by reducing the pupil size and cutting down the
amount of light hitting the retina and in turn the amount of red-eye
bouncing back from the eye.
Both features could be disabled,  the red-eye, through the function buttons,
and the auto focus part could be disabled by using manual focus, or ensuring
that the flash didn't pop up during auto focus, or by using manual settings.

Brian..........................