Dashed Flash
One technique that I have used for years with my film cameras is to place a small slave flash unit in a scene to even out the lighting. Recently I tried to do the same thing with a simple digital camera and was shocked to see that, although the slave flash was triggered, it had no effect on the captured image. What is going on here?!
David Braun
Via e-mail
Your slave flash was almost certainly triggered by the preflash that your camera fired to determine exposure, not by the burst emitted by your camera while its shutter was open for the actual exposure. Because the second flash happens only milliseconds after the preflash, there’s inadequate time for your slave flash to recharge. A moderately priced alternative to your older slave flash would be the little Metz 28 CS-2 Digital ($130, street). It’s slave-activated, with a self-learning Easy mode that automatically ignores a DSLR’s preflashes.
Guiding Light
Something in the Lighting column (“Bright Ideas,” April 2006) confused me. I’m of the old school, where flash guide numbers were stated in “X in feet” or “X in meters.” Your statement that the various flashes’ guide numbers were “131 at 50mm” gave me no idea of their power. Would you be so kind as to explain what “131 at 50mm” means?
Robert Strang
Regina, SK, Canada
It means the guide number is 131, usually at f/1.4 and ISO 100, and always in feet. (Americans don’t cotton to the metric system.) The lens focal length of 50mm was once a given for determining guide numbers, but then came zooming flash heads. Now, a handful of flash makers inflate the implied performance of their flash units by using zoom heads racked out to 100mm or 105mm. It results in narrower—but longer—throw, and, yes, a higher guide number. In today’s market, it’s wise to learn the focal length (and sometimes ISO, too) at which a guide number is established before comparing flashes.
More Flash
I have a new Canon EOS Digital Rebel XT and an old Canon Speedlite 60F. Can I use this Speedlite without harming the camera?
Edward Meyerson
Via e-mail
The 60F Speedlite was sold as a companion flash for the old manual-focus Canon T60 camera. It had an extra flash contact for setting shutter speed automatically, but otherwise performed autoflash using strictly an external sensor—sort of like a Vivitar 283 or 285. It should be useable on a modern Canon EOS camera, although only in the Manual or Av exposure mode, if you manually dial in the aperture suggested by the flash. Because your Digital Rebel XT can take up to 250 volts, there should be no trigger voltage issues using the 60F.
|
