Usually when I am using my flashgun it is to provide some additional light or light from a different direction so there is usually enough light for the autofocus to work. When it gets a bit darker the focus assist beam is supposed to fire. Unfortunately this is not happening. I have obviously messed about with the camera settings somewhere but I can’t find it.
I had to use manual focus for this shot and with view finders that are intended for autofocus use they don’t give much help. Back in the days of manual focus the viewfinder would be split into several areas with different kinds of focus help. My Yashica of many years ago had a centre split image where the lines on the subject would appear disjointed unless they were in focus and this was surrounded by an area that would appear speckled unless the image was in focus.
Now all you get is a beep and/or a flashing square in the viewfinder when the camera thinks it is in focus.
I have been through the settings on my camera and the one that seems most relevent is custom Fn III ‘Autofocus/Drive’ setting number 11 ‘AF assist beam firing’. It is set to’enable’. I have tried ‘disable’ then back to ‘enable’. But it still does not fire.
I should add that in fully automatic and CA modes it does fire but in the Program and manual modes it does not. The instruction manual has a nice, easily understood table which shows that the assist beam is automatic in the Full auto and CA modes but selectable in the other modes. (At least now manuals come as PDF files so you can pretend that you never actually have to succumb to RTFM.)
If/when I find out how to get my camera to behave itself I will add to this posting. If anyone knows the answer pleas let me know.
Update: I posted this question on the Canon forum and got the response that the beam will only fire when the camera is set to ‘One shot’. This makes sense of sorts. I normally have my camera set to AI Servo or manual because I shoot mainly wildlife. If the subject is moving then using focus beam assist will not give good results. The subject needs to be stationary, in this situation the focus mode should be One Shot. C1, C2 and C3 on my camera are all set to One Shot.