On-camera flash adds light to the subject, so the image is sharp and recognizable, but it is also flat and lacking in texture, depth and artistic interest. Adding one or more additional flash units, placed off camera, does much to improve the quality of the image. This can be done by adding slave sensors to conventional shoe-mount flash units or by using studio-style flash equipment, but the exposure will need to be computed manually. Advanced flash features in many SLR cameras and flashes eliminate much of the drudgery and yields accurately exposed multi-flash setups easily. We’ll explain how it operates with Canon and Nikon cameras. The Pentax K10D and Sony Alpha A100 also offer wireless remote flash. As a general rule, only specific flashes made by the camera companies for their SLRs have wireless control capability. Few independent flash makers include this feature.

MULTI-FLASH WITH NIKON EQUIPMENT
Multiple flash begins with a master flash mounted on and controlled by the camera, and one or more auxiliary SB-600 or SB-800 flashes serving as remote flashes. The flash built into the D70, D70s, D80 and many other Nikons (but not the D40, D40x or D50) will function as a master unit, or an on-camera SB-800 Speedlight can serve this purpose. The master flash communicates with the remote units, using pre-flash pulses to control output instructions.

If using the built-in flash as the master, set it up as the “commander” on the camera mode. If a Speedlight SB-800 will be used as the master, use the flash’s “custom” menu to set it as that, then select the channel you wish to use for all the remote flashes. If you want all the remote Speedlights to contribute the same amount of light, use the same channel number for each unit. If you want different units to generate differing amounts of light (from -3 to +3 EV steps), select a different group (A or B). For example, you can have one unit providing main illumination and set on 2 steps more light than the on-camera master and another unit adding fill to the background set on -1 step. 

MULTI-FLASH WITH CANON EQUIPMENT
With Canon’s multi-flash system, a Speedlite 580EX on any current Canon digital SLR is used to fire other 580EX or 430EX Speedlites that are positioned remotely. Up to three groups of units (such as main, fill and background) can be set up with output adjustable over a 6-step range. Unlike Nikon, the flash built into the camera cannot function as the master. Setting up the master and remote flashes is similar to the Nikon system.

POINTS TO KEEP IN MIND
When using wireless multi-flash, position remote units closer to the subject than the camera so their sensors will pick up light from the master flash. Make sure the remote flashes are within line of sight to the master unit, and within the range indicated in the instructions, usually 15-25 feet. When positioning the remote units, don’t let direct light from the flash be directed to the camera lens or you will have inconsistent exposure and possibly lens flare. Always test-fire the arrangement after setting up all flash units to make sure that all units are triggering properly when the master unit fires.

 Take advantage of the outstanding multi-flash technology that is built into today’s cameras and flashes to enhance your flash photos.