Committing to a lighting setup - thoughts

[tirediron]

...All of my speedlights and strobes I've used have built-in phototransistors right from the factory that allow them to simply fire whenever the lighting changes rapidly enough (another flash going off on the subject). It doesn't require any 3rd party stuff, and it works very reliably...

Until you have that speedlight and it's optical sensor inside a large softbox, or similar modifier.

 

[Overread]

Two problems with triggers based off light detection are irregular results in strong lighting - a hit and miss thing some will be good and some won't be. I've used a cheaper optically triggered flash and sadly found that whilst indoors it was great, outside in the sun it just would not pick up the other flash firing.

The other problem is that some subjects will see the first flash (optical triggers typically pick up the first -oft invisible to our eyes) flash telling them to fire) and will move before your main beam can fire. This does tend to be insects on the whole, and not all of course. But I've had a fair few flies who will jump up and even with a single flash firing direct from the camera they can pick up the ETTL first beam and you get legs (if you're lucky) in the shot.

 

[Gavjenks]

Until you have that speedlight and it's optical sensor inside a large softbox, or similar modifier.

Yeah I do that fairly often, and it works. Even with double diffuser layers.
I offer no guarantees and do not recommend this if you are in direct afternoon sunlight or anything like that. But indoors or at night when I would usually be using multiple lights in the first place (not just a fill), I've never had it fail.
Note that the key light should be the one you trigger by radio or wire, to provide the maximum signal to the others, since it's the brightest.

The other problem is that some subjects will see the first flash (optical triggers typically pick up the first -oft invisible to our eyes) flash telling them to fire) and will move before your main beam can fire. This does tend to be insects on the whole, and not all of course. But I've had a fair few flies who will jump up and even with a single flash firing direct from the camera they can pick up the ETTL first beam and you get legs (if you're lucky) in the shot.

I can't speak to the reflexes of insects, but personally as a human I cannot even perceptually detect the timing difference, much less have anywhere near enough time to flinch, etc.
From what I understand about how the technology works, it should essentially trigger at (the speed of light) - (any tiny circuit delay) - (whatever time it takes to get the second strobes through the majority of their output curves / capacitor discharge).
Which is usually something like 1/500th of a second, and can be much faster if needed (nearly 1/10,000th of a second for strobes and up to 1/20,000 or less for speedlights)

Maybe flies can react that fast, and that's what you're talking about.

But again, I'm a little concerned that we aren't talking about the same thing, since you're using language like "beam" which makes me think coded infrared beam triggers which is not what I'm describing. Those are slower since they usually transmit a modulated signal that takes time, not just "any light go Go GO"