Check what?
Well to check the sharpness of an image I just captured, I play it back and zoom in on it to see how good it is. I've since gotten into the habit of this since realising my 450D has poor quick-AF, and really it's good practise because you just can't tell if a photo is decent on a 3 inch screen without zooming.
To do contrast-detect AF in live view, you have to turn it on in one of the custom menus. Can't remember where but it's under 'custom function' somewhere. You'll see a bit about focus in live view, you want to turn on CONTRAST DETECT AF, and not Quick AF. Then to do it you press the 'zoom out' button on the top right of the body when in live view. You'll hear the lens seeking, and after a few seconds, providing the light is acceptable, you will have a perfect focus lock. I'd help you just now but I am at work with not a camera today.
Hope this helps?
Sorry, "Check" meant "check if it's enabled"
Spotted it, it's called "Live mode" in the manual for some reason. It's only applicable to focussing in Live View though.
Thanks for explaining, most helpful

