What is a slave flash?
A slave flash is a flash that is triggered by another master flash. You may have noticed event photographers with assistants carrying flashes on poles. These are slave flashes which are triggered by a primary flash on the photographer’s camera. The typical reason for using a slave flash is to illuminate your subject more evenly by providing flash light from multiple sources. There are several approaches to triggering a slave flash. Some have sensors that monitor for a primary burst of flash light and then respond with their own flash. Others are controlled by radio signals from the primary flash. You need to put some thought and research into the type of slave flash that will be best for you. In principle, slave flashes with sensors are the most versatile and will work with any flash system. However, there is a complication: Some slave flashes can be triggered prematurely be red-eye reduction systems or by preflash metering systems, Canon’s E-TTL for example. Before purchasing a slave
