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I have a Sony hot-shoe flash that can be triggered remotely by the on-camera flash.

Are there strobes for umbrellas/soft-boxes that I can reliably trigger from the on-camera flash in the same fashion, thereby saving the cost of a hot-shoe wireless trigger and receivers? If so are there any drawbacks (other than the fact that other cameras in the vicinity can trigger them)? Are there any standards that describe this compatibility?

Update: Do all strobes have a light trigger option? If so then is it not sufficient to ensure just one fires — e.g., by making sure my Sony speedlight is in the mix at a desired (low-power) strobe location — on the assumption that a real flash will set off all the others?

(Note that I'm not asking for TTL info; I'm willing to set strobe intensity manually.)

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    you can buy light triggers that fit to the hotshoe connector of the strobe very cheaply. In the UK I bought one from Jessops for under £3, so if the strobe doesn't have the function to do that built in. The main issue surrounding reliability is likely to be ambient light. The darker it is, the more reliable the light trigger is likely to be – laurencemadill Jul 17 '14 at 8:55
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    adding to my comment, about half way down this page: bcsdigitalimaging.com/camera-accessories.html is a minicell slave unit that has hotshoe on top, product code 1091526. This looks exactly like the one I bought very cheaply. The item above it looks like can be mounted separately so it can 'see' the master unit better but would need a sync cable – laurencemadill Jul 17 '14 at 9:00
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You're talking about a number of different things here. But first off, using your Sony HLV flash off-camera with your pop-up as master is a different system than typical "optical slaving." While this is optical and light-based, it's a proprietary signalling system that uses a series of light flashes to communicate information (which is why this system can support TTL, HSS, and remote power control), rather like morse code light blips. This is multiple pre-flashes, and that will typically make this system completely incompatible with any other "dumb" (manual-only) optical slave system, like the one you'll find on most studio strobes/monolights (which is what I'm interpreting you mean by "strobes for umbrella/softboxes; speedlights can use umbrellas and softboxes, too, y'know and also classify as strobes).

However. Nearly all monolights, even the cheap Chinese ones, typically come with a "dumb" optical slave sensor in it. It's rarer to find them in speedlights, but quite a few of the 3rd-party manual-only flashes incorporate them, too. This basically works as a sensor that turns a fast bright light pulse into an electrical signal that sets off the flash. The only signal it can convey is the "fire" signal, so it's a manual-only trigger. And it can be tripped early by any pre-flashes, although some of these slaves are now built with a way to fire on the second flash it sees, so it can use a master flash signal that's TTL with a single pre-flash (i.e., in whatever flavor of TTL your camera system uses, but NOT in "wireless master/slave" mode, which would emit multiple preflashes).

The drawbacks are the usual ones with any optical triggering system: range, line-of-sight, and being overpowered outdoors. The sensor must "see" the light signal. If there is anything blocking the master signal from the sensor panel, the signal won't get through, and it won't fire. Outside in bright sunlight, the signal might be overpowered and not register highly enough over the ambient light, and the signal is lost. And if the master signal is very far away, again, the signal might be lost. These triggers work best in studio conditions, where there are bounce surfaces to relay the signal if there's no direct line of sight, and where the master flash pulse will be considerably brighter than the ambient lighting.

This is why we like radio triggers; no line-of-sight requirements (just a lack of radio interference), and the range and reliability are better than with optical slaves--especially outside in the daytime.

Studio strobes also typically do not have PC sync ports--these days they mostly seem to use 3.5mm headphone minijacks/plugs to convey the sync signal.

See: Strobist posts: A walk around the Monobloc, pt. 1, and pt. 2.

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Can you share with us which strobes you want to fire? It all comes down to the connections they have. With PC sync you are safe. The triggers themselves are low-tech light sensors, so I suspect it will be possible in most cases.

As for drawbacks, you mentioned that any flash will fire them. Also, the light that triggers them will need to be directed at all the strobes. If one's sensor is obstructed, it won't fire. A third is that the on camera flash light may make it into the photograph. If it is directed straight forward, it has probably the least aesthetic quality. But the more sensitive hot shoes will be triggered at little power from the on-camera flash. I often trigger them at 1/64th power of my Canon 430EX.

  • Still shopping, but from what I've read so far I don't want to go "cheaper" than an AlienBees. I don't want to be tied down by a PC cable. My Sony Alpha body has a wireless flash mode where I assume it either fires the on-camera flash at low power or prior to opening the shutter since it's sending TTL info. – feetwet Jul 17 '14 at 8:06
  • I meant a PC cable between your strobe and a hot shoe/light sensor triggers, which could be only a few cm/inch. – Jeroen Kransen Jul 17 '14 at 8:21
  • Confused: Are you talking about a bona fide wireless trigger system (which I wanted to see if I could save the cost of)? Or is there something in between that consists of a light sensor independent of the strobe that connects to the strobe? If the latter could you provide an example? – feetwet Jul 17 '14 at 8:24
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    Sorry if I used the wrong terminology. What I meant is a slave trigger with a light sensor and a pc sync output. I googled quickly, and here are some examples: scantips.com/lights/slaves.html – Jeroen Kransen Jul 17 '14 at 8:30
  • Something like this maybe: ebay.com/itm/Vivitar-Flash-Slave-Trigger-Unit-SL-1-PC-Sync-/… – Jeroen Kransen Jul 17 '14 at 9:05

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