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Jim23 · Posted: Mon May 24, 2004 3:20 am Post subject:

Will x-sync at 1/500 "clip" the light output on higher-power flash units set for Manual operation? After years of using a Metz 60CT flash, I finally read the instructions recommending 1/125 sec. shutter speed with a leaf shutter. I am in the habit of using this flash on Manual with the Compur shutter at 1/500 sec. and have been noticing a tendancy for underexposure by a stop (but still very printable on b/w shots).... I wonder if on these higher-guide-number units on manual or with studio flash, the longer duration at full-power requires a slower shutter speed? I always used 1/500 sec to avoid ambient light ghosting with indoor action shots. On fractional power settings or automatic, the duration is much less and this should not be a problem; however, with the 4x5 Crown Graphic, it's great to take a group shot on TX 320 speed film, be back 20-25 feet, and still use f16.

RichS · Posted: Mon May 24, 2004 3:29 am Post subject:

Yes

Many electronic flashes will slow down to 1/300 or so on full power output. This is sometimes stated in the specs for the flash. So you could get away with 1/200 or 1/250, but 1/500 will underexpose on most of them. 1/125 is obviously the safe speed...

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t.r.sanford · Posted: Mon May 24, 2004 1:51 pm Post subject:

Might not one say, rather, that a relatively high-powered flash like the Metz "60CT" will have a flash duration of about 1/300 sec., and the duration gets shorter when you reduce the intensity (say, by using the automatic exposure feature)?

The Quantum "Q-flash T1" produces a 1/300 sec. flash if you do nothing to shorten it, and if memory serves, my Honeywell "Strobonar 892s" also delivered a flash of 1/300 sec. duration.

Of course, the rise and fall times are very fast, so I'd imagine that you could catch the whole flash at 1/250 sec., if the X synchronization really is tripping the flash when the shutter blades are open all the way.

Nick · Joined: 16 Oct 2002 Posts: 494

I know my 45 at full manual power is supposed to be 1/300 of a second. It takes quite a bit for ambient light to make a difference. With a powerfull flash I'd doubt that the indoor room light would get noticed if you set the shutter at 1/125. If you have a flash meter it might show what percentage is room light versus flash.

I always thought the high speed shutters were more for outdoor fill flash. Indoors at F/16 you'd need a fairly long shutter speed. The flash overwhelms that room light at 1/125 or even slower.

BTW When you attach the flash cable to the camera make sure the flash is off. Don't ask me how I kow-)

t.r.sanford · Posted: Mon May 24, 2004 7:56 pm Post subject:

True. I've done a great deal of trade show and other indoor work with a 35mm. focal-plane shutter camera whose X synch speed is 1/60 sec. or longer, and a Honeywell handlemount flash set for auto exposure at f:11 with 400-speed film (black and white, later color).

Only when the ambient lighting contained fairly powerful spotlights did it ever have any real effect on the pictures, most of which were made at distances of 6 to 15 feet or thereabouts.