Thanks to Mark Wallace, I’ve been seeing a lot of workshop/web tutorials about this little known feature on some high end flashes. Of course, if you started out in photography when I did, that was the only option besides manual control of flash. None of this fancy E/i-TTL stuff. The advantage of this is that you have a mode between line of sight TTL optical triggering and full manual radio triggering. You can use a dumb radio trigger (ebay/Cybersyncs/Pocketwizard Plus II/III) and yet still have some automatic light control when flash to subject distance changes, all without two way communication between body and flash.
Basically, there’s a little light sensor built into the front of the flash. Nikon (top of the line at their time) SB-28, SB-80DX, SB-800, SB-900/910, etc have them and the Canon 580 EXII has one. I’ve got several Nikon SB-28s that I use for off camera flash stuff, so this example shows how to use it on an SB-28.
When you set the flash mode to “A” it will give you distance guide (similar to Manual mode). When you first turn on the flash you have to set the ISO, it will blink for about ~5 secs when powered up. This is the only time you can change it. Once ISO is set, you can use the +/- buttons to select the Aperture you want to use. The distance range that the flash can adjust itself will change as you can see below. Zooming will also change those distance values. However, once you rotate or bounce the head the distance guide indicators will disappear.
The sensor will not work when it is blocked by anything, so you are pretty limited to using it bare, or a limited number of modifiers that allow the light sensor to see light bouncing back from the subject. I’ve got a Lastolite Umbrellabox that fits the bill perfectly, but most reflective umbrellas should work too. You need to leave the sensor exposed and facing the subject while the flash head is pointed where necessary.
Here’s some test shots with it, I moved the light up and further away, yet it was still able to maintain similar, if not exactly the same, exposure without any intervention from me. The exposure at the camera was the same in both shots, 1/200 F4.0 ISO200.
I’ll have to experiment with this on some portraits to see how well it work, but the results are promising so far.
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