I just purchased a new Canon EF 200mm f/2.8 L II for my EOS 3. I have yet to finish my first roll of film with this lens but I love it already - the feel and build are superb.

However, I don't know what the focusing distance range switch is doing for me. Set on 1.5m to infinity, I can focus through the lenses full range. Set on 3.5m to infinity, I can not focus closer than 3.5 meters.

I understand what the switch does - I do not understand why. What advantage is gained by limiting my focusing to grerater than 3.5 meters?

I know someone out there knows - thanks in advance for the info.

Derrick

-- Derrick Morin (morin@fttr.navy.mil), July 12, 2001

Answers

When the focus button is depressed the camera and lens undergo a focusing cycle. This involves the lens moving the focusing elements within the lens; the camera detects when focusing is achieved and the camera tells the lens to stop moving any further. In difficult situations the camera finds it difficult to detect when the image is in focus (low light, poor image contrast, through glass etc.) the lens then 'hunts' back and forward to try and achieve focus. To 'hunt' from 3.5m to infinity and back takes half the time of 1.5m to infinity and back. When rapid focus is essencial the time saving may be crucial.

-- John Rochester (rochester@homeshef.freeserve.co.uk), July 12, 2001.

John,

Your explaination makes a lot of sense - probably a very smart feature. Thanks for your input.

Derrick

-- Derrick Morin (morin@fttr.navy.mil), July 12, 2001.