70-200L F/4 IS and the closer-focus switch

While taking pictures of my 70-200L (which, as you will be able to tell I have used almost not at all -- I knew I wanted a 100-400 when I bought the little brother), I noticed a switch that allows the lens to focus as close as 1.2m, or thrown the other way, up to 3m or so.

The obvious difference in distance aside, does one setting have greater merit than the other? I suspect so, or why would the lens have the switch, but what is the merit?

Mcooper450 wrote in post #4968745
The obvious difference in distance aside, does one setting have greater merit than the other? I suspect so, or why would the lens have the switch, but what is the merit?

It's basically there to keep the camera from false focusing on something in the foreground, and also keeps the camera from racking back and forth through that range when it's hunting.

From the owner's manual:

"By setting the suitable focusing distance range, the actual autofocusing time can be shorter".

Thanks for the replies.
Mike

Not sure if the replys you have got so far really answer your question, but the switch is there to tell the lens whether you want to focus closer than 3 m or not.

If your shooting at longer lengths, you can put the switch at the 3m position, and it tells the lens to not focus on anything closer than that.

As the autofocus is pretty quick with this lens, I'm not sure how much time it really saves if the lens starts to hunt, my questions is whether or not it will extend the usm's life to keep it from doing so through its entire range when not needed.

It probably doesn't make any difference, but I should have indicated that my lens is the f/4 IS version.

Again, thanks for the insights.
Mike