EF 300/4 focusing distance selection

[juhhyto]

Can someone please explain, why there is two selection for the focusing distance (1.5 m to infinity and 3 m to infinity)? I do understand the meaning of the button, but why to use second one because first one includes the second one?

[tommykjensen]

It is because, if You know You subject is farther away than 3m You can save a little focus time if the lens does not need to consider the area 1,5m to 3m.

Why this rather small area have that significant meaning I don't know. Because You could ask Yourself then why not have a switch at 5, 10 & 20 meters for example? Perhaps someone else can answer that question?

[gasrocks]

Like anything else....try it and see what diff it makes when you select either setting (for normal shooting.) It does take quite a while for the lens to hunt up close and back to inf. so, I am sure 3m was chosen as a pratical cut off point for everyday subjects. Just another button to impress someone with, and to remember how you last set it!

[Tom W]

If you look at the focus scale, 3 meters is roughly in the center of its travel. So if you set the switch to 3-infinity, the focus mechanism will only have to cover 1/2 of the total travel range needed to obtain focus. Unless, of course, you manually focus at less than 3 meters.

[Medic1]

As said above.....once you start learning when to use each one you will find them beneficial (well, depending on what you normally shoot)