I just purchased one of these new model lenses and have a question.

This newly designed lens has what has been referenced to as a second diaphram used to control flare. What I've seen while focusing the lens while it's not on the camera is a diaphram like opening which disappears when the lens is focused at infinity, but appears before 1:5 macro ratio is reached in the focus range.

Basically, what I want to ascertain, is this the 2nd diaphram that's referenced, or is my actual "taking" lens aperture not opening up fully to f/2.8.

Anyone have this lens, and if so, will you check the thing while it's off the camera to see of yours does the same thing. Just curious if this is the 2nd diaphram.

Regards

-- Elda (elda@ticnet.com), April 10, 2001

Answers

I have the 100 USM macro, and I see the same thing you described with my lens. I don't know whether this is the 2nd diaphram or some other lens phenomenon. My lens works perfectly for portraits and close ups, so what you describe seems no cause for concern.

-- AC Gordon (cliffdeb@ciris.net), April 30, 2001.