A big part of light control with Speedlites is making flash go through something -- anything from a colored gel to large devices to soften light. Syl gives a run-down of many of the options available.
• If you are using more than one sender, the color of the <LINK> lamp will vary depending on the order in which you turn the senders on. The first/main sender is green. Subsequent/sub-senders are orange.
Press the 600EX-RT’s Select/Set Button, and turn the Select Dial to choose any one of five settings. P.Fn-02 – LCD panel illumination color – Normal on-camera flash 0: Green
In this mode you set each receiver unit to a fixed output and set the camera exposure manually. You can set each unit to the same or a different output. This mode is ideal for lighting setups where the flash-to-subject distance is fixed and you want your exposure setting to be consistent from one shot to the next—for example, when you are photographing subjects in the same scene whose color and reflectivity are variable.
