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Zeiss Contax Distagon 28/2.8 Aperture

G

Guest

Hello. I've just bought the S2 together with the 1,4/50 and the 2,8/28 lenses. I have a question about the apperture on the distagon 28. Is it not supposed to be hidden totaly when apperture 2,8 is choosen? For me it is visible, rather much. And also, there seems to be no difference in apperture size between f16 and f22. That is, there is equal ammounts of light through apperture 16 and 22. Is there anyone with any idea of what could be wrong?

Regards Kent
 
G

Guest

I'm not quite clear on what the problem is. Do you mean that when you have the aperture set at f2.8 the iris is still partially closed rather than wide open? And that when you close down from f16 to f22, the aperture stays at f16? If so, you've got a lens problem. As it happens, the only lens I've ever bought new that had a mechanical fault was the Zeiss 28mm f2.8. It froze at f2.8 and had to be sent back to the factory for repair under warranty. Only a shipping charge, I believe.
 
G

Guest

this is exactly what I meant. The equipment was used, and have a couple of years on its back. Therefore I have no warranty anymore. But at least I now know that this lens is supposed to behave like all other lenses I've seen. I guess I have to open it up and check out the aperture machanism. I will also check with Contax service to see what can be done in the matter. Thanks for the answer.
 
G

Guest

this is exactly what I meant. The equipment was used, and have a couple of years on its back. Therefore I have no warranty anymore. But at least I now know that this lens is supposed to behave like all other lenses I've seen. I guess I have to open it up and check out the aperture machanism. I will also check with Contax service to see what can be done in the matter. Thanks for the answer.
 
G

Guest

Kent,

>I will also check with Contax service to see what can be done in the matter.<

I will be interested in what you find out. This is exactly what I have with my D28.

Alex
 
G

Guest

It seems that no one have heard of this before. When I opened the lens I only took away the aperture ring. And there seems to be nothing wrong with the mechanism so far. I didn't remove the lensgroups to dismantle the aperture. Although I might do this since the cost for a repair almost matches the cost for a used lens anyway. The aperture blades seems to be clean, so I don't think thats the problem.

Alex, have your lens been this way all time, or have there been any incident causing this?
 
G

Guest

Kent,

>have your lens been this way all time, or have there been any incident causing this?<

It's always been this way, but it was not new when I bought it, and is out of warranty. The lens itself (MM model) is in very good condition otherwise, optically perfect, no barrel markings or wear of any kind. I noticed it more or less by accident because the exposure readings I was getting showed around 2/3 stop slower than my Planar 50, so I got all the lenses out and all the bodies out, and compared meter readings (fairly unscientifically). The Distagon 28 always showed slower. So I looked closely at the aperture blades, and at f2.8 they seemed to still be there are the edge of the lens, where the other lenses I have showed only glass.

I did contact Kyocera UK and they told me to send it to Contax in Germany, but I haven't done that, since what I hear from this list is that I'd be cheaper buying another. Exposures themselves seem to be fine, so I can live with that, and I don't think I have the courage to open a lens. It's just mildly annoying that a CZ lens should be 'out of tolerance' like this.

Alex
 
G

Guest

Do the aperture blades do the same thing with the lens mounted on the camera? You can operate it and see by holding the DOF preview. I seem to remember something like this, though my memory is very fogging. I may be off but it's worth a try. Jeff
 
G

Guest

Jeff,

>Do the aperture blades do the same thing with the lens mounted on the camera?<

When I put the lens on the camera, I can see the aperture blades when it's set to f2.8. When I press the DOF button, the blades move in and the aperture shrinks. Definitely not what I expected.

Alex
 
G

Guest

> > it's set to f2.8. When I press the DOF button, the blades move in and the aperture shrinks. Definitely not what I expected<<

Ya, that doesn't sound right. I remember I had a lens (can't remember which one) that the blades were visible until it went on the camera, then they retracted that tiny bit so evrything was as it should be. It's probably not much and just needs a service. I know a few repair places that have been good for me but they're in Canada, and I'm sure that's no help. Good luck, Jeff
 
G

Guest

>Sounds like the connection between the aperture ring and the aperture blades is assemled wrongly, or was demaged by an external shock. If you can not return the lens to the seller I'd recommend you to clarify the price of repair. I suspect that fixing this misfunction is something like 'disassembling+correct assembling', or may be replacing a single mechanic detail. It should not cost much.

Sergei
 
G

Guest

Hi, Alex,

I had similar problem with one Distagon 2,8/28. May be only the aperture unit and blades must be cleaned in one good service place or from specialist with absolutely good experience – there is may be a little dust and oil. If the lens is old, or not used long time, or was sometime in high temperature area, this can be “expected” problem.

Valentin
 
G

Guest

Sergei,

>I'd recommend you to clarify the price of repair.<

Thanks to you and Valentin and Jeff and others for the suggestions on repair. I have just gone into town half an hour ago and deposited the lens with my local dealer (not where I bought it, which was in London), and he reckons that a disassembly-re-assembly should be all that's needed. If no parts are needed, the cost should be around GBP40 ($60), he says, so I've told him to go ahead. I should have it back in about two weeks. This is a reliable dealer to whom I've been going for around sixteen years, so I have no qualms about giving him the lens. I'll let you know how it goes!

Thanks again to all,

Alex
 
G

Guest

Hello all. And thanks for your replays. I've also done the test comparing exposure times with my 1.4 planar. Using my f1,4/50 at aperture 2.8 for a white paper give me 1/125s exposure. For aperture 2,8 the f2.8/28 gives the exposure 1/15s for the same paper.

There is no difference if the lens is mounted on the body. Pressing the DOF button moves the blades to a smaller aperture (smaller hole).

Talking to the swedish service place gave me a price suggestion around 110-160€. Therefore I decided to disassemble the lens myself. Hopefully a cleaning will be sufficient. I'll post back here when I've come to any conclusions.

And thanks again to all
/Kent
 
G

Guest

I've disassembled and reassembled my lens now. The aperture mechanisms only needed a little turn and now it works like a charm. Thanks all for your help.

/Kent
 
G

Guest

Kent,

>I've disassembled and reassembled my lens now. The aperture mechanisms only needed a little turn and now it works like a charm.<

You may recall that I had exactly the same problem, but gave to my local dealer to repair rather than risk t&ering myself. I've now got mine back too (it was only away three days), and it is now perfect. Diaphragm works flawlessly, and meter readings are spot on and line up with my Planars and Sonnar. It cost me a fixed repair charge of 40 pounds ($60), which means that the total I've paid for my D28, which I got second hand, is almost the same as full price for new. But I'm still pleased, as the lens was otherwise in mint shape anyway. I'd put off repairing it before because of tales that Kyocera would charge as much for repair as for a new lens, but thanks to a suggestion on this forum I went ahead with a reputable local dealer, and I'm glad I heeded the advice.



Alex
 
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