The difference between Master Enabled and Master Disabled is a simple and essential concept for Speedliters shooting wireless flash. Yet, many Canonistas (myself included back in the day) draw the understandable conclusion that Master Disabled means that the master is not a master. It’s an understandable, but incorrect, conclusion.
Master Enabled means that the master will send instructions to the slaves and also fire when the shutter is open (adding flash to the shot).
Master Disabled means that the master will send instructions to the slaves and then remain dark with the shutter is open.
Deciding When to Enable and Disable the Master Speedlite
Master in the Camera Hotshoe: Choose Master Enabled only if you want to have on-camera flash (say a bit of low-power fill flash). Choose Master Disabled if you do not want the shadow-killing effects of on-camera flash. In both cases, the master still sends instructions to the slave Speedlites.
Master Moved Off-Camera: If you have an extra-long ETTL cord, then you can move your master Speedlite off-camera and use it as Master Enabled. The advantage of this technique is that for the cost of the cord, about $65 on OCF Gear or Amazon, you can get valuable off-camera light from your master and still have it control the slave Speedlites. If you become a power Speedliter, you will eventually want a dedicated tran$mitter. But an extra-long ETTL cord is a great way to maximize the gear you have right now.
How to Enable/Disable the Master Speedlite
The easiest place to enable/disable a master Speedlite is on the LCD of your camera. If you have a 580EX II or 600EX-RT and a 40D or newer Canon camera, then you can access the entire Speedlite menu on the back of your camera. Head to the External Flash Function menu and then to the wireless menu. [See this article for tips.]
If you have a 550EX or a 580EX (original model) or an older camera body, then you must disable the master on the Speedlite itself. To do this:
- Activate the Speedlite as a master (Use lever on 550EX and 580EX. Press and hold Zoom button for 3-seconds on 580EX II and then turn Select wheel).
- Press the Zoom button and the zoom setting will flash.
- Press the Zoom button again and the Ratio setting will flash.
- Press the Zoom button again and the Channel setting will flash.
- Press the Zoom button again and the Master Enabled/Disabled icon will flash. Turn the Select wheel to on/off as desired. Press the set button in the center of the wheel.