How limiting is Canon’s optical wireless flash system for off-camera portrait lighting?
Asked 11/21/2011
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I’m using a Canon 7D with a 580EX II and want to start doing off-camera flash portraits. The 7D’s built-in wireless flash control uses an optical signal from the pop-up flash. How restrictive is that in practice? For example, will a flash in an umbrella positioned to the side or front-side of the subject still trigger reliably if the flash sensor is not directly facing the camera? Can I reasonably rely on the 7D’s built-in optical triggering, or is line-of-sight such a limitation that I should expect to need separate triggers?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
5
The flash is triggered by the popup-flash of the 7D.
The signal is transmitted by light, it is just way too fast for the naked eye to see. The popup flash would strobes rapidly, like sending out morse-codes, and the external flash would pick it up and fires in sync. The whole thing is super fast, like in 1/500 of a second.
Understanding that, you now know that the limitation of such approach is that when the light is too weak, it will not reach the flash, and the external flash will not fire.
Another situation is that, when the surrounding it very bright (under direct sunlight for example), the popup flash is relatively weak, and the "morse-code" signals cannot be properly detected by the external flash.
Reducing the distance between the popup flash and external flash should solve this.
I use the 60D, and it has the same system too. I do not do a lot of outdoor daytime shot, I usually have a cable with me should I need off-center external flash. However I use the wireless flash system indoor very often. It is sufficiently reliable when you are in an indoor settings. Provided that you have some walls to bounce some of the light around, it really isn't a must that the flash must be at line of sight.
Ultimately, in an indoor settings, in a small room, I can place the external flash anywhere I want, and it fires no problem. If your portrait work focus on indoor shooting, its absolutely fine.
Finally, you already have the 7D, you do not seem to have the flash unit yet. You must buy a flash regardless which wireless option you choose, right? So why don't you buy a good flash unit, try out the wireless function on the 7D, then decide if you really need other wireless solution?
Originally by user6745. Source · Licensed CC BY-SA 4.0
user6745
14y ago
0
Generated from our catalog & community — verify before relying on it.
Canon’s built-in wireless system is optical, so the 7D sends control pulses from the pop-up flash that the 580EX II must detect. It’s not strictly “sensor pointed straight at camera or it won’t work,” but it does depend on the remote flash being able to see that light directly or via reflections.
In practice:
- Indoors, it often works well even when the flash is off to the side, because walls/ceilings can bounce the control signal.
- The receiver on the flash can usually detect light from a fairly wide range of angles.
- Small rooms with light-colored surfaces are easiest.
- Large spaces, dark walls/ceilings, or setups designed to absorb stray light can reduce reliability.
- Bright ambient light, especially direct sunlight, can make optical triggering much less reliable.
- Shorter distances improve success.
So yes, a side-positioned umbrella setup can work fine, especially indoors. If you’ll shoot outdoors, in bright light, or need maximum reliability regardless of placement, separate radio triggers are usually the better choice.
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