Canon 100mm Macro (non-L)

How is the AF with ceiling light ? Mine is hunting a lot. Is it normal ?

Mine doesn't, but what type of ceiling light? One bulb and rather dark in the room?

No, I have 5 60W chandeliers-type bulbs. When I set to f/2.8 it did not have problem but at f/8 it kept searching for a point to focus.

And the TV was on too, so it wasn't dark in the room at all.

Mine hunts often in the macro range, almost never with distant (1:5 or less) subjects with limiter engaged. f/8 vs. f/2.8 should have no effect -- the camera focuses with the lens wide open either way, only closing the aperture with full press.

Mine does that whenever focus is in the macro range and I tried to focus on something that isn't. I find it easier with mine to just manually focus until the subject is somewhat in focus, then let the AF take over. I figure it makes it easier on the lens and it's motor since there such a large range in it's focusing.

Yeah, I agree.... Since the lens always focuses at the widest aperture, it should make no diff if you have f2.8 or f8 selected as the aperture for your exposure. The lens only stops down at the very instant of exposure, so that has no effect on AF.

There is a focus limiter switch on the 100/2.8. Using that will speed up focus quite a bit, by keeping it from going off hunting in the range you aren't using.

It's going to differ, too, depending upon the camera body, as well as the focus mode you have selected. If you manually pre-select only the center AF point on most EOS, it should focus faster. That's a more sensitive AF point with lenses f2.8 and faster. If you use All Points or manually select one of the outer points, expect it to AF slower. Different cameras use different AF sensor systems, which will perform more or less well in dim light. 7D and 1D series have a dedicated processor for AF. The other cameras share the processor among other functions, including AF.

Finally, your subject will have an effect on AF responsiveness and speed. If it's a nice, contrasty edge you will see faster focus than a subject will little contrast or detail.

Any macro lens' focus mechanism has to travel a whole lot farther than a non-macro lens', so it's to be expected that a macro lens will focus a bit slower. The 100/2.8 USM in particular really isn't bad, but isn't quite as fast as some other, non-macro lenses (85/1.8, 135/2, 70-200 for example).

With a USM lens, yes it's a good technique to manually focus the lens into the ballpark, then use AF to finish acquiring focus. That usually works. Just don't try that with any of the non-USM lenses! You'll damage the AF mechanism. It needs to be turned off at the switch prior to manually focusing the lens. USM lenses have Full Time Manual focusing (FTM), which allows you to override the AF without switching it off. (There is an earlier, non-USM version of the 100/2.8 macro, among others.)

Look like I'm not ready for macro world . I guess I'll kiss my birthday present goodbye since I'm more into flash now. Going to break the news to my DH . Thanks all.