Sonnar 180 f/2.8: faulty?

[cn]

Dear fellows,

I have a Zeiss Sonnar 180 f/2.8 for Contax/Yashica, AE version made in Germany, with the straight barrel (newer design), and find it a little strange. When shooting outdoors recently, I discovered it wouldn't focus to infinity, i.e. if an object is rather far away (1-2km), I can't get the lines of the split prism to line up.

First, I suspected temperature to be an issue, so I tested again indoors (looking through the open window, but with the camera at room temperature). The issue is not so evident in this case, but even if I line up the lines in the split prism as precisely as I can, regardless of distance, I always have a "flickering" image in the microprism ring. Comparing with my closest lens, the Sonnar 135 f/2.8, I cannot reproduce any of this on the latter. Here, mechanical infinity is always optical infinity, and once something lines up in the split prism, it's dead smooth in the microprism ring.

Is there something about the design of the 180 that causes these effects, or do I have a bad lens? Would someone who has this type (or the MM version, which should be largely identical) be able to comment?

Thanks a lot!

[aoleg]

Do you have another camera to try it on? Maybe a digital SLR with Live View?

[cn]

No I'm afraid, just two film cameras with split-prism and microprism ring, and a bunch of lenses (all with shorter focal lengths, and only one of them is a Sonnar), plus a Mutar III.

[calvin83]

This lens features floating element design for aberration correction at close range.

If your lens have problem on both of your camera while other lens do not. I would suggest you give it to a professional for checking and repairing.