0.31m - Infinity

[Octoshark]

My Canon 100mm macro has a little switch next to the focus control that has two options:

0.31m - infinity
0.48m - infinity

I messed around with them a little to see what changed, but didn't really notice any difference. What exactly does this setting control?

 

[Octoshark]

I think I found the answer:

On the left side of the lens barrel (viewed from above) there are two little switches. One is for AF vs. MF. The other one can limit the focusing range. There are two settings: you can either use the full range from 0.31m to infinity or a restricted range from 0.48m to infinity. The second setting will speed up focusing significantly if you use the lens as a 100mm telephoto lens instead of as a 100mm macro lens as it will not hunt for focus in the very close range between 0.31m and 0.48m

So I guess only use the 0.31m for macro shots and switch to 0.48m for portraits, is that right?

By the way thanks for all the help everyone here in the photography forum gives out, its been very useful.

 

[Recty]

Yep, that is the correct answer

I only have one lens that uses that and I use it only for long distance photography so I never set it down to the broader range of focusing.