Re: filmscanners: (OT) Flash durations, was Pixels per inch vs DPI

["Mark T." <markthomasz@ozemail.com.au>]

Just for the record, for those who don't use *studio* flashlighting, 
*on-camera* flashguns rarely drop below 1/500 second flash duration, as 
Dave said.  (Just checked 3 different flashgun manuals to make sure my 
memory serves correctly..)

In fact, the cheaper and smaller the flash, generally the shorter the flash 
duration.  Only high-power flashguns (eg the 'hammer' type generally seen 
hanging off Bronicas, Hassleblads, etc) get down around 1/500 and they get 
there only when you need an awful lot of light..  So compared to the lowest 
fully-open, ie synch-able, shutter speed of a typical SLR it is still a 
much shorter duration.  I doubt that any latency would be relevant - I 
mean, you can slave a second flash off an electronic eye, and *still* not 
catch the second shutter curtain...

And before anyone asks, I'm not going to any effort to prove it - I got 
over all this stuff when I first learnt about cameras.. ;-)

You simply *must* use the synch speed or less (or experiment to see whether 
they have erred on the low side - eg on my usual SLR, the synch speed is 
1/100, but I've satisfied myself that 1/125 is actually still OK).  At 
1/250, hardly surprisingly, I don't get a full-frame of flash - for the 
reasons already explained in some detail..

mt


From: SKID Photography <skid@bway.net>
>For the record, we use ProFoto studio lights, where we've
>experienced the 250th of a second cut off of
>lighting output on our Polaroids.