Help with Canon EF 100-400mm L lens

[ryder]

I just received my new lens and have read the booklet that came with it and am very confused by one setting. They tell what the switch does, but do not explain when and why you would use one setting or the other. The setting I am stuck on is the "focusing distance range" and it has two settings. One is 5.9 ft to infinity and the other is 21.3 ft to infinity. So what are the advantages/disadvantages of each choice??? The booklet is unclear and confusing. HELP!

[LoveDSLR]

Originally Posted by ryder

One is 5.9 ft to infinity and the other is 21.3 ft to infinity. So what are the advantages/disadvantages of each choice??? The booklet is unclear and confusing. HELP!

This is a focus limiter to improve AF performance. Use the 21.3 ft to infinity setting if you don't need to focus closer than 21.3 ft.

[Raoul Isidro]

Using the 21.3 ft to infinity will limit the lens to "hunt" at this setting. It does not have to go all the way back to the closest focusing distance, which doing so losses precious micro seconds, specially in fast action shooting.

[ryder]

Thank you both for this. I think I get it now! Sorry for the newbie question, but I just was being thick headed. This wonderful community comes through again!