100mm Macro, Marco to Distance AF?

[GerBee]

I've a one year old but rarely used 100mm Canon Macro.

Pleased as punch with it when I use it, expect for one little ditty. If I focus on a flower and then try and focus on a street scene, the lens won't AF.

I can turn the AF ring an as I approach the focus for the more distant street scene the lens snaps into life again and focuses fine. Is this normal behaviour for this lens?

Cheers
:eek:

[PaulB]

Quite normal as the AF doesn't have enough contrast to lock on to when the scene is so far out of focus - bit like trying to focus on a grey card, no edges, no contrast.
That's why the lens has a focus limit switch so that it can't waste time trying to run from one end of the range to the other when the subject is very close or very distant.

[GerBee]

Great, thanks.

That makes perfect sense :):):)

Quite normal as the AF doesn't have enough contrast to lock on to when the scene is so far out of focus - bit like trying to focus on a grey card, no edges, no contrast.
That's why the lens has a focus limit switch so that it can't waste time trying to run from one end of the range to the other when the subject is very close or very distant.

[Pete]

The lens doesn't have the fastest AF. So when you're focusing close on a flower, and then want to focus on something in the distance, the lens is so out of focus that it takes a while to get itself sorted out. Repeated pressings of the AF button are sometimes required.