Monday, 6 August 2012

How to Trigger your Off Camera Flash

We have discussed On camera flash and the disadvantages it has like causing red eye, flat looking images with no depth etc. The best method to counter these issues is to move your flash off camera. Believe me, moving your flash off the top of your camera will result in a quantum leap in your photographic skills. Once you have control over the position of your light sources, you will be able to control the shadows, enhance the shape, reveal texture and create depth in your pictures. It should be noted that moving your flash just a short distance away from the lens has a huge difference on the feel of your picture. In this article we will discuss how to trigger your flash off camera.

Standard PC Sync Cord for Off camera flash
Standard PC Sync Cord for Off camera flash

There are many ways to trigger your flash off camera.

Option 1. Wired connection:

This is the most basic connection of all and it involves connecting the camera and the flash using a sync cord. It may be a standard PC sync cord or the more advanced ETTL or ITTL cords.

Standard Pc Sync cords are the least expensive option, they could be easily modified to any length so you can place your flash unit as far from the camera as you wish. However they only perform the function of triggering the flash and nothing more, it won’t communicate with your camera and so you will have to manually set the exposure values and if you need to either increase or decrease flash power you will have to walk to your flash and do it manually. Another serious disadvantage of a standard pc sync cord is that it allows you to connect only a single flash unit.

ETTL or ITTL cords are the more sophisticated versions of sync cords. They enable the flash unit and the camera to communicate with each other and determine exposure values. More over you would have full control of your flash unit right from your camera menu. No walking over to your flash to adjust power. However the functionality comes at a price and the standard length of ETTL or ITTL cords are Two feet. There are extra long versions of these cords available in the market from third party manufacturers also which have a length of five meters or more.

ETTL / ITTL Sync Cord for Off camera flash
ETTL / ITTL Sync Cord for Off camera flash

Physically connecting your camera and your flash with a sync cord has it disadvantages too. First there is limited flexibility then there is the issue of a wired mess (people tripping on wires) and more.

Option 2. Optical connection:

The second method of connecting your camera and flash unit is by using an optical device, commonly referred to as ‘optical slaves’ or ‘optical triggers’. They consist of a circuit with a light sensing diode which triggers the flash attached to it when it sees a pulse of bright light (another flash or strobe).

Optical Triggers for Off Camera Flash
Optical Triggers for Off Camera Flash

The main advantages of optical slaves are that they are cheap to buy and have no wired mess. However it also has its disadvantages firstly it will not function properly in a brightly lit scene as it has to see the pulse of light to trigger the flash. That also means that they only work when placed in line of sight of the main light. Secondly they too cannot transmit ITTL or ETTL information making it a manual mode only set-up and also making adjustments difficult. Thirdly when there are more than one photographer working on scene the unit will fire the flash with any flash of light it sees (not necessarily yours).

Option 3. Wireless triggers:

Wireless triggers are the preferred method of professional photographers for triggering off camera flashes. There are two types of wireless triggers available ones that use Infra-red light to trigger and the ones that use Radio frequency to trigger flashes.

The Infra-red transceiver:

(Transceiver – A unit which could transmit and receive information)The two major camera manufacturers, Canon and Nikon have their own proprietary optical triggering mechanism built into their advanced flash units. Allowing one unit to be set as master and be able to control other units set to slave mode via the master flash.

Infrared Trigger for Off camera flash
Infrared Trigger for Off camera flash

 The main advantage of this set-up is that it has full ETTL or ITTL capability without any cords. However the major disadvantage is that as it uses infra-red light to communicate between each other the units have to be placed in the line of sight of each other. The second disadvantage is that of limited range.

Radio transceiver:

Until recently the option of using radio transceiver sets to trigger flashes were not available from the major camera manufacturers. And photographers depended upon various third party accessories to trigger their flashes using radio frequency. The major brand among them is the Pocket Wizards (PW). Where in you attach one unit on top of your camera’s hot shoe and attach the other to the flash unit via a sync cable. You could attach any number of flashes this way and set them in different groups and control their output from your on camera unit.

Radio transceivers for Off camera flash
Radio transceivers for Off camera flash

Radio transceivers are superior to optical transceivers in many ways, they have extended range, they need not be placed in line of sight (you could trigger around corners, walls etc), they could be set to multiple channels in cases where more than one photographer is using such units etc.

Canon Flash 600 EX RT and Speedlite ST E3 RT
Canon Flash 600 EX RT and Speedlite ST E3 RT

The latest flash offering from the Canon stable the canon 600ex-rt speedlite has built in radio transceivers that enable it to control other flashes (same model). The Speedlite ST-E3-RT can trigger up to 15 Speedlites over distances as far as 30m.

In the next article we will discuss about Photography - Lighting - Flash - Slow Sync Flash

Related Reading

  1. High Speed Flash Synchronization
  2. Focal Plane Shutter
  3. Types Of Flash Synchronization
  4. Flash Synchronization
  5. Flash Guide Number