So, how do you set off, or trigger your flash so that the brief pulse of light is synchronised with the camera shutter opening? Predictably, you’ve got lots of choices, ranging from cheap and simple, to expensive and quite complicated.
Triggerring on Camera
First off, you can of course trigger your flash by having it attached to the camera. This will offer you the most control, and may well offer you the use of modes like TTL exposure, as well as handy info like a “flash ready” light in the camera veiwfinder. The catch is of course, that your flash is on the camera, so your lighting options in terms of direction are pretty limited! On a geeky note, the flash is here attached to what is called the “hotshoe” on the camera. This is a standard mount you can find in lots of instances – they’re often used to attach microphones for video as an example. It’s called a hot shoe rather than a cold shoe, because it allows some form of information to pass between the flash and camera. In some cases this can be as basic is “fire/don’t fire”, but in most modern cameras it also includes the ability to pass metering information and the like between the two. A cold shoe simply functions as a mount – it doesn’t exchange any information. There you go – free geek points.
To move your flash off camera, the simplest and cheapest way is to buy a “PC” or sync (synchronisation) cable, plug one end into your camera’s PC socket (you may need to buy an adapter for your hotshoe if your camera doesn’t have this socket) and then the other end into your flash. Again, you may need an adapter for your flash, as not all flashes have a socket to take a sync cable. Cables like this are cheap, less than £20 usually, and pretty reliable as long as you’re careful with them – they’re useless if you crush the PC end, which I’m ashamed to say I’ve done quite often. Make sure you buy the right connector for your flash – some take a mini headphone jack, others a large one, and some require the opposite/male end of a PC cable. You may be able to simply stick a jack adapter on to a smaller headphone plug at a pinch.
The 2 drawbacks to just using a simple cable like this are the fact that your camera and flash are now attached – you can’t place your flash very far away without a LOT of cable trailing everywhere, and the fact that since it’s just a simple cable, all it will do is trigger the flash – you won’t get any control over power output, or be able to use exposure modes like TTL. Since they’re so cheap and reliable though, I always carry some, and you often find they come as part of the basic kit with your flash.
If you want to retain some control over triggering, and use modes like TTL, then you’ll need a dedicated cable. These must be specific to your camera and flash – you can’t for example use a Nikon flash and camera with a Canon cable – they won’t talk to each other. This allows you to shoot in modes like TTL, if the fancy takes you, and may allow you some degree of control over flash output from the camera. The catch is that you’re still cabled, and therefore attached, and that theses cables (for what they are) are quite expensive. On average they retail for about £60.
Most larger flash units, and some flashguns, come with a slave mode. This is a superb piece of technology that functions as a basic optical trigger. Built into the unit will be a sensor, which simply triggers the flash to fire when it sees another flash. The speed of light means that the happens pretty much instantaneously, so everything syncs up. The big plus to this is that now you can start to position flashes wherever you like – you’re not bound by a cable anymore. If you’ve got a multi-flash setup, then you can simply trigger one flash directly from the camera, and the rest can all be in slave mode – you just need the one trigger.
What’s the catch? Well, predictably there are a few. First off, it’s just a simple optical trigger – all it will do is tell the flash to fire, or not fire – nothing more than that. You can’t adjust power outputs, or get any feedback from remote units. Secondly, it relies on line of sight to work, although you can sometimes find they’ll pick up flashes if they’re placed carefully. This means that they’ll only work over a certain distance, and perhaps won’t work when tucked away behind objects or if they’re in a different room. Lastly, they’re so simple that they can be set off unintentionally. If someone else fires a flash, all yours will go off. If an emergency vehicle drives fast with it’s lights going, there’s a decent chance yours will fire, and so on. Just be prepared, and you should be able to work round this. An optical slave is an incredibly useful thing to have in a flash unit – all mine have them, and besides anything else, their simplicity allows you to mix and match units of different types. For example, I can have my flashgun mounted onto my camera like you see in the video, and have my Profoto head set to slave mode, and the flash from my Nikon flashgun will set off the flash from my Profoto. Very handy.