Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 200)

E-TTL Balance
You can set your preferred appearance (balance) for flash shots. This setting enables you to
adjust the ratio of ambient light to Speedlite light output.
Set the balance to [ Ambience priority ] to lower the proportion of flash output and uses
ambient light to produce lifelike shots with a natural mood. Especially useful when
shooting dark scenes (indoors, for example). After switching to <
> mode, consider
setting [ Flash sync. speed in Av mode ] in [ : External Speedlite control ] to [ Auto ]
and using slow-sync shooting.
Set the balance to [
Flash priority ] to make the flash the main source of light. Useful for
reducing shadows on subjects and in the background from ambient light.
Caution
Although [ Ambience priority ] is effective in dark scenes, there may be no
difference from results with [ Standard ] in some scenes.
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