whats this dial for?

hi have a 17-85 lens.It has a dial reading from macro to infinity.Is this to control the depth of field?If so would setting to a low number produce a storytelling image and infinity a singular image?thanks in advance

Is it the focus limiter switch? I don't know if the 17-85 has one, but they are normally used to limit a lens' focus range, so the intended focus is over a smaller area and thus - faster.

Or are you talking about the focus ring?

jc450d wrote in post #9431583
hi have a 17-85 lens.It has a dial reading from macro to infinity.Is this to control the depth of field?If so would setting to a low number produce a storytelling image and infinity a singular image?thanks in advance

Focus ring?
P.S.
Yes - I found an image of the 17-85. What you are looking at is the distance scale that shows how far away the lens is focussed. It will change as the lens changes focus, either automatically or when you use the focus ring manually.

Depth of field is primarily controlled by aperture (wider aperture -> shallower DoF and vice versa), but there are other factors.

Did your lens come with the instruction sheet? If so you might want to read it. Lots of good info there.

No focus limiter on the 17-85, it doesn't need one as the AF is really fast. You are looking at the distance scale. It shows what distance the lens if focused at.