Flash triggers

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    To inaugurate this section: What do you use to trigger your off-camera lights at RE? I’m guessing you have some sort of radio-trigger system. Or are you using an infrared controller?

    Being at the dSLR low end, I currently use the pop-up flash to trigger my off-camera lights via the built-in optical slaves. I also have the block-the-pop-up-flash gizmo (’cause it was cheap…) I see a lot of recommendations to go to radio triggers, but that’s a low priority for me, given the small spaces (hotel room, living room) I shoot in.


    Hi Lurker,

    We most commonly use the Hensel studio flash kit’s own radio-based flash trigger system:


    The portable power packs have a receiver for this built in, which allows us to remotely adjust light intensity, which can be handy.

    The older flashes don’t have the built in receiver, so we use the plug in one shown in that pic. Can’t use it to adjust remotely, though.

    Generally it is enough to trigger one flash and use the slave system to trigger the others, though this can cause problems in large dark spaces. Fortunately the built-in system in the newer kit gets around that problem.

    We don’t use this exclusively. Sometimes we use a cheap and cheerful IR system, which can work when the lights in the black studio are struggling to trigger each other on slave and we’re trying for rather subdued low light patterns. A generic one does just fine, it is just an old fashioned manual flashgun with an IR-only filter on the front anyway!


    Indoors, we’ve actually found this to be the most robust solution. Outdoors, especially in bright sunlight, it can be utterly blinded and hence useless. The radio seems to have slightly better range, but that can be tenuous too- we have had issues with triggering especially outdoors if the lights are quite far away. We got a fair few mis-triggers on this set:


    I’d say my experience with the radio system is that marginally better than the IR, but for shooting indoors there’s very little in it. I don’t know if I would have bought it had it not been built in to the flash packs!

    We also sometimes use on-camera flash to trigger the rest of the lights. That’s particularly useful if you need catchlights in the model’s eyes, but you need to beware of burning out anything that gets too close to the camera when using on-camera flash. I tend to use a Canon Speedlight set to manual as it gives me some control over that as I move around, but will use the pop-up at a push.

    This one is particularly useful on location where we might have limited lighting kit with us- I used the on-camera fill to trigger quite a lot in Scotland.

    The one thing that I never use is a sync cord. I remember the days of having to use them, absolute nightmare of trips, tangles and pulling over lights. Whatever you use, a wireless system is a must if you move around as much as I do when shooting.

    I’d say you’re absolutely fine with the triggering system you use now, Lurker, unless you find yourself burning out skin tones when you come in for a closeup. If you do, an IR trigger will do the job, but a radio one might be more future proof if you ever think you might shoot outdoors.

    Cheers, Hywel.



    What’s the delay in the radio and infrared trigger systems? I’d expect an optical system to be extremely fast, a radio system somewhat slower. Is this even a problem or does everything happen much faster than the mechanical shutter anyway?

    I know film SLRs had to use low shutter speeds (e.g., 1/125 or slower) with electronic flashes because at higher speeds only part of the film frame is exposed at any instant. I presume the shutters in digital SLR cameras are similar?


    The delay is not significant for normal studio use in either radio or IR systems. You’re looking for the start of a great big signal, and you can do that easily and cheaply with electronics that responds at sub milliseconds timing. The electronics isn’t doing anything complicated, just
    REPEAT (check input)
    UNTIL (input jumps up by enough to trigger)
    Fire flash

    And that’s basically the same whether you are triggering from sync cord, IR or radio. Only the delay in sending the original signal will be different because IR has to trigger a flash and radio has to send a radio “beep”.

    Here’s a test:


    showing that the pocket wizard system introduces delays around 0.7 milliseconds, or around 1/1500 th of a second. That’s not likely to be the limiting factor for most shooting setups. It might come into play if you were using ultra-short shutter speeds with extremely short duration flash. Presumably guys that need 1/4000th of a second exposures would be using kit with faster response times.

    Most digital SLRs do indeed still have the two-curtain sync system which limits the flash sync speed. They make their exposure by firing two curtains- the first one opens the shutter, the second one closes it again. To generate short exposures, they fire the second curtain closer and closer to the first one. At around about their flash sync speed, there’s no longer a time when the whole aperture is fully open- the second curtain starts to close the shutter before the first curtain has cleared the top of the frame. This is cheating- it makes short exposures by making a strip of light which it moves across the sensor, rather than by just opening the whole shutter up at one go.

    Flash is generally fast compared with this, so you get a “band” or see the shadow of second curtain starting to close if you exceed the sync speed. Actually with the Canon dSLRs we generally turned it down from 1/200th (the nominal sync speed) to 1/160th because in a few studios we started to get second curtain shadowing:
    (Which shows me I didn’t do a good enough job getting rid of it in post processing- bad form, Hywel 🙁 🙁 )

    Medium format cameras traditionally have leaf shutters in the lenses, which open a circular hole. They aren’t capable of shutter speeds as fast as a two-curtain focal plane shutter (typically 1/800th of a second) but at least they are fully open when they are open, and so can sync with flash at any shutter speed. With our Hasselblad you have to adjust the exposure a little at 1/800th (because the leaf shutter works like having a smaller aperture while it is opening and closing, so a bit less light gets through than you’d expect) but the system is entirely robust and allows us to use 1/400th of a second or faster routinely. This helps with sharpness.

    More recently, dSLR’s have started using a combination of electronic and physical shutters. These can sync up to very high speeds in principle- they open the physical shutter for say 1/125th of a second but only read out the chip for for a very short time. Using this for fast flash sync is outside their intended use so might be a bit hit and miss but there are reports of cameras being successfully used with studio flash at 1/8000th of a second or faster: shorter than the duration of most flashes. That’s a place where timing issues on triggers could start to creep in.

    Cheers, Hywel.



    Thanks, Hywel. Your posts are always very informative!

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