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Trouble with using Zeiss 50mm/1.7 ae with Contax RTS II



hello everyone
i'm a little confused about my new lens.
i recently inherited a RTS II with 35mm and 85mm lenses. i loved the images from these lenses so much, i decided that it would be worth it to invest in a used 50mm to bridge the gap. i've been told often that 50mm in any brand, usually is the sharpest. i was very excited to hear this since i've done up to 16x20 prints that were very sharp and acceptable 20x30 prints with the lenses that i already own. the problem is that the 50mm/1.7 that i received in the mail does not work correctly on my RTS II. it looks very clean, including the blades, the action is smooth on both rings. the lens fits on the camera nicely and the viewfinder shows the correct f-stops as i turn the ring. however, the camera sticks when i fire the shutter. it is actually the mirror that jams. i decided to try this thing with the mirros locked up. and the shutter fired at the bulb setting precisely. but when i release the mirror lock up switch, the mirror did not come back. the viewfinder was blacked out and i could not shoot. in regular manual mode the mirror just sticks and the only way to get it down is to unlock the lens. i did notice a difference in shape of the metal part at the back of the lens between my 35mm MM lense and this 5omm AE lens. is there any way around this problem? or am i stuck with an amazingly sharp lens that i cannot use? please help. i could go out and hunt for a different 50mm but now i am afraid that this will happen again....


Well-Known Member
Hello Dong,

Unfortunately your RTSII has "mirror crept". Over time, the mirror slides forward just enough to touch the rear of the lens. Do not attempt to fire the shutter too many times as it may touch the element as well! It doesn't happen to all lenses as there are different lengths that the lens protrudes past the mounting flange. Usually happens mostly when the lens is focused at infinity (rear most) setting.

I just sent my RTSII to Kyocera of NJ about 6 weeks ago for the same problem and am awaiting its return with a complete overhaul (as they put it). It will cost you around $185 to get this fixed. If it hasn't seen a CLA for the last 20 years (since it's introduction in 1982), it would probably be a good time to do it now. I should be receiving mine back in a couple of weeks and will update contax info when it arrives.

Regards, Gary >


I know the disappointment you have from not being able to use your new lens. If I can make a suggestion as to the problem. The only coupling that Y/C lenses have that goes to the mirror is the one on the bottom of the lens. The one that closes the blades when your shooting less than fully open. The lever part on the lens should make contact with the lever on the body only at their edges. If the lever on the lens rides up past the edge and the flat part of the lens lever is on top of the flat part of the body lever you will get the condition you've described.
It's quite a serious problem if that is what's happening. The lens will mount, but with more than normal effort. If done with too much force, the lever on the body will be bent and break. That happened to me.....
The solution could be as easy as straightening the lens mount or as disappointing as giving up using the lens on the camera. The lens may be incompatible with your particular body, but may work on another, due to differences in tolerances.
The lens mount is the weakest mechanical part on Y/C lenses.
There's a discussion here that applies to your situation. It's about the aperture not reading correctly and the problem residing in a bent lens mount ring. The lens mount ring is very thin. It's held on by three small screws. If it's anything but flat is can cause all sorts of problems.
Good shooting


thanks for you input.
i'm not going to put this lens back on my camera.
i'll just keep it for a yashica body that i'm planning to acquire as a back up. and thanks for the "mirror crept" tip. i never knew this camera even had such an issue. i don't think this camera has seen a technician since it came out of the box, but it also has not been used much. do you think this can happen in storage? well, at least i know the option of getting it serviced, which is always good for the camera so i have no complaints about that. thanks guys