I have a EOS Rebel XS & a Speedlite 430EXii. The AF Assist Beam only works on full auto.

[napacat]

I thought the AF assist beam would work on all custom modes, I use the TV mode most since I like shutter priority, but it doesn't focus in low light. Can someone help me out? Is it a camera, flash, or setting problem?

[Skirball · Accepted solution]

It should work fine in Tv mode.  However, it won't work if your autofocus is set to AI Servo.  Check the setting and change it to One Shot.

If that doesn't do it double check the custom functions, but the majority of the time people have trouble with AF assist it's because they're in AI Servo.

[napacat]

THANKS VERY MUCH!!!!!