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What is the Slave Function and how do I set this up?

When multiple studio flashlights are used, it is common for one flashlight to be connected to the camera through a cable or a wireless trigger set. It is then possible for all additional flashlights to flash simultaneously through the use of the slave function setting. This function works through the use of infrared light sensors, which are built into all studio flashlights. When the first flash is released, the infrared sensors of the surrounding flashlights are triggered and flash simultaneously.

Slave Function Problems

As the slave function works through the reaction of light released from the flashlight connected to the camera, numerous factors can reduce the reliability and accuracy of the flash lighting. When the studio flashlights are used in conjunction with a softbox, it is possible that the softbox covers the infrared sensor and therefore blocks the signal to release a flash. Regardless of this, majority of the time the flashlight still works due to the adequate lighting distributed evenly through white walls and ceilings. However, when there is a lot of external lighting, the light released from the connected flashlight is generally not strong enough for the sensor affecting the accuracy of the slave function. In addition, it is possible that the light sensor reacts to the flash of other cameras surrounding the workspace.

How to Overcome these Possible Problems 

If there is too much external lighting such as photographing outside, the only solution is to forget the slave function and connect each studio flash unit to a trigger set. Most trigger sets have additional receivers in order to connect your desired number of studio flashlights.

In a studio where the external lighting is controllable, there are more options in regards to overcoming sensory issues. It is most important for the flashlight connected to the camera to be visible to all other sensors of the flashlights. Generally the flashlight furthest away should be the control flashlight connected to the camera in order to send the light signal to the other sensors. If this doesn’t work, it is also possible to connect additional receivers to the other flashlights that can’t reach the sensor. In all cases where you decide not to use the slave function, it is important to turn the slave function off. This way the flashlight will not go off randomly or react to the initial camera flash.

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