A bad Jupiter 12?

[Carburo]

I've a Jupiter 12 in Contax/Kiev mount, but I'm absolutely not satisfied about the results.
My Kiev's rangefinder seems to work fine with the Jupiter 8, the Jupiter 3 and - I hope - with the Zeiss Sonnar f/1,5 that is shipping to me.

In my opinion my Jupiter 12 is always blurry and offers low contrast.
I would like to have a feedback from you about it

May be a focusing problem? I remember I've read in a post about fixing problems like this on a Jup12 with DIY operations, but I can't find it.

Than, if I'll realize that it's an unlucky one, I'll replace it with another one.
Just want to try...

Can u suggest something?

Here you can see some examples:

http://www.carburo.altervista.org/003.jpg
http://www.carburo.altervista.org/001.jpg

[pshinkaw]

My experience with J-12's is that they are not high contrast lenses. Your examples look typical for contrast. However, the blurriness is NOT normal.

-Paul

[denishr]

It might have been me with J12 problems and focusing - I've solved them in the meantime by inserting 2 thin paper shims between the body and the back (protruding) lens element.
From the examples you provided I can't offer much advice... What you should do is try to take some shots on close distances, like 1 - 1,5 m.
Include a spread newspaper in the shot, or a tape measure, so that you can see where the sharpest (focused) area actually is. Oh, and use full aperture (2.8).
After such test, you'll be able to see whether it's a lens alignment problem, or you simply have a bad example.
A quick check: make sure the back element of the lens is screwed all the way - maybe it got unscrewed a bit. The back element has the usual (standard) right hand thread, so screw it all the way in.
Apart from that, I'm afraid you'll have to do some test shots as I described above. For test subject you can also use stuff like playing cards stacked one behind the other in a row, spaced about 5-10 cm apart, or something similar. Another useful target is ordinary (picket) fence - put markers on top of the spikes, so you know which is which. The most important thing is to determine where the focus actually is - which isn't evident in your shots.

Denis

[denishr]

This is one example test shot, which I did when adjusting my Jupiter 12. It's the central part of the omage only. Enough to see where the actual focus is - e.g. the sharpest numbers on the tape measure, middle business card, etc... Use whatever you have at hand, even spread newspapers, as I mentioned will do...

Denis

[doubs43]

Originally posted by Carburo
In my opinion my Jupiter 12 is always blurry and offers low contrast.

First, make sure that the front and rear sections of the mount aren't loose. There's a collar that keeps the two sections together and it can be seen from the rear. There should be minimal play between the front and rear sections. Tighten the collar if necessary.

If nothing is loose, the best way to solve your problem is to use ground glass and a loupe of 8x or greater. With the Kiev back removed, mount the camera on a tripod & lock the shutter open on the "B" setting. Tape the ground glass to the film plane, making sure it's not on the higher upper and lower rails.

The rear element of the J-12 unscrews so loosen it. Back it out a few thousands of an inch and check the ground glass (focus set at infinity) to see if the image is sharper. It becomes a matter of trial and error until you find the correct setting for the rear lens element. Then cut and insert the proper thickness shim and you're in business! Mine required almost .030" which I made out of plastic.

Good luck.

Walker

[Carburo]

Thanks all you for the help.
I'll try to do my best and I'll keep you in touch.