When you get to the point you want to use more creativelighting, is when you need to advance from the on camera external flash to more powerful and flexible studio flashes (aka studio strobes). Those flashes are triggered either by wires connected to your camera's sync terminal or by a wireless trigger, called slave.
There are two main types of slaves:
1. Optical slaves
2. Radio slaves
The optical slave is either integrated into your flash system, or plugged into the sync terminal of your flash. When an optical slave senses the light of another flashit instantly fires the slave flash. This method is simple to use especially if your studio flashes integrate an optical slave. However there are three main disadvantages in using optical slaves:
1. Integrated optical slaves have a very limited sensitivity for distance and light angle, which makes them almost impractical for outdoor use or complex multi-flash setups in the studio. You can buy stronger and better optical slaves and overcome this obstacle, but they cost a lot.
2. Optical slaves are sensitive to any flash in their territory. Any one with a camera that takes a shot near your flash might activate the slave and you may find yourself taking a flash-less shot while your flash is still charging from another person's shot. Bad idea...
3. If you are also using an on camera flash that meters light by a pre flash (evaluative flash), the optical slave may be activated by the pre-flash. Then when your shot is actually taken, the flash will not fire because it's charging from the pre-flash shot...
So the other and more comfortable way of wirelessly triggering your flashes may be by radio triggers. The prices for those systems vary from a few USD, to few hundreds for a single device...
On the top end level you will find professional products like Quantum Instruments Radio Slave 4i Set. On the bottom you will find various Radio slaves sold on eBay. The main differences between the expensive ones and the cheap are:
1. Effective range.
2. Ability to control the frequency.
3. Build quality and durability.
4. Reliability!
If you are looking for a strong, professional and reliable radio system, and you are willing to pay the price, go for Quantum or Pocket Wizard systems. They truly offer the best solutions for a pro, in any situation, including remote triggering your camera (used for sport competitions and more...). But I promised to talk about the inexpensive alternative so let's focus on the cheap radio slaves.
Advantages: Price, Size, weight.
Disadvantages: Range, Reliability.
Let's say you have 3 self powered strobes (monolights) that you want to use in your home studio. Your work meets the following characteristics:
1. Indoor location.
2. Short range.
3. Accessibility to backup equipment such as sync cords in case of malfunction of the radio trigger.
4. Not a "once in a lifetime" type of event (such as a wedding).
In that case, you may find the cheap slaves very useful. You buy them in sets of transmitter+receiver, so in your case you would buy 3 sets. This leaves you with 2 spare transmitters already. In my experience with those gadgets, the most common fault is a transmitter going dead in the middle of a session. This may be caused either by low battery power, or by the poor quality of the product... So if that happens, you can immediately switch to a spare transmitter, and leave the battery issues for later after your session ends.
Given those working conditions (stress less, amateur to "easy pro" assignments) you may actually find the cheap slaves more fun to work with as they are lightweight and smaller. Ienjoy using themwhenI'm shooting inside my studio.
Here are three tips that will help you extend the usability and reliability of your cheap slaves:
1. Remove the sticking out test button. Most of the transmitters are equipped with a small test button that is sticking out of the transmitter case. Most chances are that it will be pushed in when you leave it in your bag, drain the battery and even damage the delicate electric circuit board. If you open the transmitter cover you should be able to remove just the cover of that button, thus leaving it still functional, but sunk in the box instead of sticking out. Don't worry; you will still be able to press that sunken button.
2. Keep a stock of spare batteries. Those Transmitters typically operate on small 12V batteries, the ones usedincar keyless remote. They are cheap, they are easy to find, and as mentioned they are also good for your car remote... the best of both worlds. Note that those thingies have a tendency to drain the battery even when not in use so always replace the battery with a fresh one before you start an important session.
3. To make it more convenient, consider throwing away the annoying screw that closes the transmitter. I suggest using a small piece of gaffer tape for a fast open-close operation. That saves precious time trying to find the matching screwdriver to open the cover, then trying to find that tiny screw again to close it...
Connecting the transmitter to your camerais done by either one of the following:
1. The on-camera Hot-Shoe. This is possible (and better)as long as you don't use an external flash attached to your camera.
2. The PC-Sync terminal, using the short sync cord that came with your radio slave system. This provides only the electric connectivity but leaves your transmitter hanging in the air, guaranteed to soon crash on the floor. Attach the transmitter to your camera/flash/strap using gaffer tape or velcro.
Here is a list of radio slaves sold on eBay shops for less then $40. Enjoy shooting!
