Lens not focusing to infinity

I recently purchased (very inexpensively) a "J.C. Penney" 35-105 f/3.5 zoom lens. It appears, to my inexperienced eye, to be made by either Tokina or one of the Vivitar sources. It's a constant-aperture, two-touch zoom with a built-in variable extension tube, and takes 72mm filters.

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Unfortunately, it seems that it does not focus all the way to infinity. The split-image focusing aid will not converge completely for subjects beyond ~30 feet. The difference is slight, and is almost always covered by DOF, but it bugs me when I'm composing/focusing. It occurs even when the extension tube is completely retracted and locked.

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I'm guessing that manufacturing slop is the culprit, either in the variable extension tube or in the mount (Minolta MC, which was obviously added on, because JCP sold lenses in many different mounts).

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Any ideas on bringing infinity back in reach?

If your lens doesn't focus to infinity it must be a little further

from the film plane than the designer intended. It's like having an

extension tube permanently in place. This could happen due to a

manufacturing defect or if the mount moved somehow. This happened to

one of my favorite Nikkor lenses once. I brought it into a shop and

they fixed it right up in a day or two. If you're interested in

keeping the lens you should bring into your local camera repair shop.

I have the same problem with a Canon FD 24~35/3.5L lens which I bought

second hand. The lens is in perfect shape, absolutely mint. It4s

really like new out of the box, so it can4t be damaged.

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It doesn4t focus completely till infinity but because of the DOF at

the focal lengths, images are still always pin-sharp. It is just

strange to see at not perfectly sharp image through the viewfinder.

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Hans Martens

www.wildpicture.com