Repeat flash in Nikon Speedlights

Discussion in 'Nikon' started by ilkka_nissila, Dec 17, 2008.

  1. Hi everyone,
    I'm thinking about doing a few test shots of small moving objects with the repeat flash feature of my speedlights. I noticed that the SU-800 doesn't seem to allow the activation of this feature remotely (CLS style). Is it possible to hook 3 flashes so that I can get a more balanced (softer) lighting while using the repeat flash feature, and if it is, what would be the best/easiest way to do it? I have a regular flash cord but only for a single flash, would the repeat flash work if I just connected all the flashes to the camera with cables?
    I'll start experiments tomorrow with a single flash and some reflectors but it would be good to know if there are elegant ways to connect several, and if the timing would work.
  2. Hi Ilkka. I take it by "a regular cord" you mean a regular Nikon cord, SC-17, SC-28, or SC-29?
    How fast is the event you're repeating? If it's not too fast, (i.e. that sort of shattering glass, splashing wine, and exploding stuff that I do) then connect one flash to the camera by the cord, set that flash to repeating at the speed and power that you want. Set the other flashes to "SU-4" mode on the remote menu, then set them to manual (not repeating) at the power you want (too much power and they won't be able to keep up). That's all there is to it.
    There is some delay, on the order of 200 microseconds, in SU-4 more. If your event is really fast, you'll have to set all three flashes on manual, and rig a simple pulse generator to trigger the flashes, and direct connect them all with SC-19 (three pin Nikon flash) or plain old PC cables.
    I do this kind of stuff with up to 8 flashes.
  3. Thanks! I will try the SU-4 mode. 200 us is a short delay to me in this case. ;-)
  4. Check page 93 of the SU-800 manual. It looks to me like you can use it to control compatible flashes and cameras in Commander mode (not Close-up). It says to hold down the SEL button for 2 seconds to change to repeating flash mode. I tried it, and that works, although I didn't try taking photos...
  5. So, what was the result of your test ?
    In SU-4 mode, each flash in the repeating sequence would be triggered separately, perhaps 200 us would not play too much of the light loss ?
    In CLS mode, only sequence Start signal would be issued, and you must hope that all flashes blink at the same time, but greater chance that any 200 usec would cause not full utilization of the light produced.
    The 200 micro seconds is pretty long time for this application. Let say if flash duration at full power is 1/1000 sec, that is a 1000 microseconds, and the 200 would be 20 % of it. However, in repeating mode you do not shoot at full power, and the flash duration is much shorter, perhaps approaching the 200 mico seconds quoted here, and that could spoil your CLS repeating test flash output registration, or even in the SU-4 repeating test.

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