How to Modify Flash Zoom on Your Canon EOS 6D
When you use a Speedlite, there may be times when you need to modify your flash zoom. Your Canon EOS 6D detects the focal length of the lens you have on the camera and sends this information to the flash unit, which sends a beam of light at your subject that has the same angle of coverage as the lens.
However, you have the option to modify the flash zoom. For example, if you’re photographing flowers with an 80mm focal length, you can set the flash zoom to 105mm, which means the flash beam of light has a narrower range of coverage than your zoom lens, which effectively acts as a spotlight. To modify flash zoom:
Navigate to the External Speedlite control menu.
Use the Multi-controller or Quick Control dial to highlight Flash Function Settings and press Set.
The Flash Function settings are displayed.
Use the Multi-controller or Quick Control dial to highlight Zoom Auto, which is the default and then press Set.
The flash zoom options are displayed.
Use the Multi-controller or Quick Control dial to highlight the desired focal length, and then press Set.
The flash zoom is modified.