My DLSR triggering wireless flash?

[skillz22]

This happened a few years ago and I've been meaning to research it, but I forgot. So I went to this event where there was a professional photographer present, and he had two or three of those wireless flash umbrella things set up around the room. I bought my Canon DSLR. I went to take a few photos and realised that the flash umbrellas... were turning on for my photos as well. He eventually told me to stop using the flash because it was using up his flash umbrellas.

 

I'm curious, how does this actually work? Do all cameras send out a signal every time they take a photo? WHat's this feature called? What form does this signal take? Just RF?

[scottyseng]

1 minute ago, slickboss21 said:

I'm curious, how does this actually work? Do all cameras send out a signal every time they take a photo? WHat's this feature called? What form does this signal take? Just RF?

There are two main trigger methods that I'm aware of, optical and radio frequency (RF). My guess is that his flashes were set to optical trigger and your flash was setting them off (They go off when they sense a flash). If the flahses were radio frequency triggered, you'd have to have a wireless trigger (Or a flash with RF support) to set them off (Even then, they would have to be paired with the master flash first).

[skillz22]

1 minute ago, scottyseng said:

There are two main trigger methods that I'm aware of, optical and radio frequency (RF). My guess is that his flashes were set to optical trigger and your flash was setting them off (They go off when they sense a flash). If the flahses were radio frequency triggered, you'd have to have a wireless trigger (Or a flash with RF support) to set them off (Even then, they would have to be paired with the master flash first).

Wouldn't there be a slight delay in the flash umbrellas that way? Since your camera times its own flash perfectly to the shutter? Anyhow, that makes sense, thanks for the info!

[scottyseng]

Just now, slickboss21 said:

Wouldn't there be a slight delay in the flash umbrellas that way? Since your camera times its own flash perfectly to the shutter? Anyhow, that makes sense, thanks for the info!

There is a slight delay, but it's so quick it's hard to tell. By far though, radio frequency triggers are better (farther range, no interference from other bright sources of light, and accidental triggers, and sync...just expensive). Optical triggers just are nice because they work with anything that has a flash (Phones, compact  cameras, etc)

[skillz22]

1 minute ago, scottyseng said:

There is a slight delay, but it's so quick it's hard to tell. By far though, radio frequency triggers are better (farther range, no interference from other bright sources of light, and accidental triggers, and sync...just expensive). Optical triggers just are nice because they work with anything that has a flash (Phones, compact  cameras, etc)

Right, thanks for the information.

[cc143]

14 hours ago, slickboss21 said:

Wouldn't there be a slight delay in the flash umbrellas that way? Since your camera times its own flash perfectly to the shutter? Anyhow, that makes sense, thanks for the info!

Sync speed is usually limited to something like 1/250th of a second, which is much less than what is necessary for the flash to trigger the other flash optically.