T90 and 135mm f/2 Infinity focus

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Hello to the list. I think I've read about this in passing somewhere, but I can't find it again. Now that I have a T90 for the first time, it's of a bit more significance. I mounted my 135/2 yesterday for a portrait of a bell tower, and it won't quite reach infinity focus. No problems with my A-1, and none with other lenses. I seem to remember there was no solution, something about the design of that lens. Wish it would focus a little past infinity like some of the others! Ideas? Thanks!

-- Alan Swartz (swartz@tyler.net), March 22, 2001


Seems something is wrong with your T90, or the lens. Check if the focusing screen is not loose. My T90 and 135/2 does indeed focus to infinity.


-- Ketil Johansen (ketiljo@stud.ntnu.no), March 22, 2001.

Either the screen is out of position (most likely), the mirror is misaligned or the mount is loose or sprung. You should be able to check the 1st one by lightly pressing the screen into place. If it's up as far as it can go then it's time for a trip to the shop.

I'd rule out the lens because it works fine on the A-1. If you still feel it's the problem, the lens can be adjusted but it's a job for someone with the expertise.


-- Duane K (dkucheran@creo.com), March 22, 2001.

I had the same problem with a 135 f2 I picked up in Canada. It would not focus to infinity. I did not try it with any other body, but the dealer had it repaired. The technician said there was no evidence of damage or previsou adjustment, so it was like that from the beginning.

May be something that is right on the edge that has a problem with T90s.

Have it adjusted and enjoy it.

-- Terry Carraway (TCarraway@compuserve.com), March 23, 2001.

No trouble here. 135/2 on T90 goes exactly up to infinity and stops. (Although I won't swear to it until something in the universe gets infinitely far away and light begins to move infinitely fast. . .)

-- Robert Segal (robertsegal@juno.com), March 23, 2001.

Thanks for all your responses. Upon further investigation, I believe I had two factors causing this. The three mount screws that secure the stainless "bayonet" ring in the mount were *ever* so slightly loose. Just enough to allow the lens to "droop" a bit under its own weight. Couple that with a warm temperature and it wouldn't quite align the split image at infinity. Tightened the mount last night, with the ring pressed securely to its maximum depth, and tried it again, with the lens cooler. It focused just a hair's breadth past infinity. New we'll see what it does in the summer. . . .

-- Alan Swartz (swartz@tyler.net), March 23, 2001.

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