Canon EOS REBEL T8i Advanced User's Manual page 222

Flash mode
You can select the flash mode to suit your desired flash photography.
• [E-TTL II] is the standard mode of EL/EX-series Speedlites that support autoexposure
flash photography.
• [Manual flash] is for setting the Speedlite's [Flash output] yourself.
• [CSP] (Continuous shooting priority mode) is available when using a compatible
Speedlite. This mode automatically reduces flash output by one stop and increases ISO
speed by one stop. Useful in continuous shooting, and helps conserve flash battery
power.
• Regarding other flash modes, refer to the Instruction Manual of a Speedlite compatible
with the respective flash mode.
Caution
Adjust Exposure Compensation
photography with [CSP] in <
Note
With [CSP], ISO speed is automatically set to [Auto].
as needed in case of overexposure from flash
> or < > mode.
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