whats this dial for

[jc450d]

hi have a 17-85mm lens.It has a dial from macro to infinity.Is this to control depth of field?

 

[Rob.Marsh]

Sounds very much like the focus ring to me. I'm struggling with the words to explain the maro markins, I'm sure someone will be along who can explain far better though.

 

[jc450d]

Focus ring at the end of the lens.This dial is close to the camera body.

 

[Mike_J_Smith]

Probably a distance scale:

"What is a distance or depth of field scale?

Most Canon EF midrange and better lenses have distance scales - clear rectangular plastic windows set into the lens barrel. A series of numbers can be seen through this window indicating the distance, in both metres and feet, from the lens to the point in focus."

http://photonotes.org/articles/beginner-faq/lenses.html#distancescale

Macro would be the closest focus distance, infinity would be the furthest. As a note macro in this sense is not true 1:1 macro, just the closest your lens can focus.

 

[jontucker]

It's just the distance at which the lens is focussed. It moves when you adjust the focus ring, yes?

 

[Chaz Photos]

Focus ring at the end of the lens.This dial is close to the camera body.

Big ring at front of lens is zoom the small one is focus this is in front of the window with the green numbers for feet and white number for meters and has the orange word macro with line under it
If this is the Canon 17-85