C.Fn #4 and #17 on 10D

[canonut]

Any and all guidance would be greatly appreciated. Here's what I'm trying to do. I have #4 set to "2" so that metering can change when in servo mode, but I'd like to be able to lock exposure in some instances, and have set #17 to "2" to lock exposure. When C.Fn 4 is set to 2, I can't use the AF stop button to lock exposure. Thanks all.

[Roger_Cavanagh]

Not wishing to offer any offence, since this is a bit of an "is it plugged in?" question. :)

CF17 is only for certain "super telephoto lenses" that have the AF stop button. I looked up the 400 /2.8 IS on Canon's site, it says:

Another feature unique to Canon's four Image Stabilized super-telephoto lenses. Four buttons appear on the outer barrel near the front of these lenses; pushing any one will temporarily lock AF if the camera is in the AI Servo AF mode. Custom Functions on many newer EOS bodies allow these buttons to assume a variety of additional functions.

Are you working with one of these lenses?

I mention this because I read the instructions for CF17 several times before realising, it doesn't apply to me. :eyes

Regards,

[canonut]

Thanks Roger! I thought the reference was to the "*" button on the camera.