I was gonna say pre-flash, I've seen that before...

On Sat, Apr 21, 2018 at 8:28 PM, Mark Roberts
<postmas...@robertstech.com> wrote:
> So yesterday was "studio shoot" day for some of my photography
> students (and some from another class). Needless to say, it was a
> massive amount of work. But it was still fun and educational.
>
> Since we had to work with a lot of students we split things up and had
> them shooting in groups of 3 or 4 at a time. We standardized the
> lighting setup with a couple of Alien Bees with umbrellas (the school
> doesn't have any soft boxes). I had every student set his/her camera
> to manual exposure, ISO 100, 1/125 shutter speed and f/8. And since
> the school only has one radio trigger we had everyone use their
> camera's pop-up flash to optically trigger the main strobes.
>
> This setup worked well. Except when it didn't. Some cameras just
> didn't get along with this and produced dark photos. In fact, some
> (not all) produced uniformly dark shots even after changing aperture.
> I'd have two students with budget Nikons set to identical
> configurations and one would work perfectly and the other wouldn't.
> (Unfortunately, due to the number of students coming through, I didn't
> have time to make a list of cameras that exhibited the problem and
> those that didn't.)
>
> After she shoot was all done I think I worked out what was going on: I
> believe it was caused by the pre-flash that DSLRs use to meter before
> the main flash. I don't know the details but I suspect the pre-flash
> was triggering the studio strobes before the shutter had a chance to
> open. Of course, when you're on manual exposure there's no reason for
> the camera to have a pre-flash at all, but it may be left on because
> the manufacturer didn't want to add additional code to the firmware
> (in the case of the cheapest cameras). The cameras that seemed to
> yield a uniformly dark exposure regardless of aperture may have been
> operating in manual mode as far as ambient light was concerned but
> modulating flash power independently.
>
> Anyway, we solved the problem by letting any student whose camera had
> trouble shoot for a while with the radio trigger.
>
> Whew. A lot of work. But very gratifying in the end. Glad the
> semester's almost over.
>
> --
> Mark Roberts - Photography & Multimedia
> www.robertstech.com
>
>
>
>
>
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