Bizarre J3 behaviour

[Assaf]

Hi guys,
I followed the recommendations from this forum and bought a J3 from a friend. The lens is in overall good condition. Aperture and focus ring are sometimes stiff but nothing too serious.
I shot a few pictures with it, I really like the look but a few of them are wierd, like the following two:

It's shot wide open, more or less minimal focusing distance. Notice that the center is in focus, but in the right side the focus is farther back, and on the left side, the focus is closer to us.
Seems to me as if the focus plane is not parallel to the film plane. What'dyou think?
If you want more pixels you can look here
http://www.flickr.com/photos/25967298@N02/3346897959/sizes/l/

Another example, also wide open, very close, my mother:

I think it's more or less the same. The hands are in focus, the red "HAMSA" palm on the wall is, but the face isn't. More pixels here
http://www.flickr.com/photos/25967298@N02/3347738486/sizes/l/

What do you say?

I can't say that this behaviour is systematic. I can just say that stopped down to F2 and taking a step back, the lens behaves better.
I overall really like the lens, and the feel it gives.
BTW, I shot with a Zeiss Ikon rangefinder and a brand new LTM-M Voitlander adapter, (type II)
Do you think it's busted? Should I return it to my friend?
Cheers
Assaf

 

[former member]

I've seen this happen when the rear module is too far out, or when the glass is not screwed down all the way. Offhand, it looks like the field curvature is too high. That usually means that one of the optics is out of place, at least in my experience.

What is the Serial Number? The 1950 J-3 that I had did something of the same thing.

 

[Assaf]

SN 5601XXX

Does it worth bothering with, or should I get another copy?

 

[former member]

I would check that the glass is loose. I had this happen with a Ziess Sonnar Wartime in LTM... It was worth fixing!

The 1950's J-3's are among the best, in my opinion. Something is causing this problem. I suspect the glass is mis-seated. Lightly shake the lens, and listen for anything loose. That's how I found out my Wartime Zeiss was messed up.

 

[Assaf]

Hi Brian, thanks a lot.
The lens doens't make any noise when I shake it.
Thinking of it, the place of the closest focus isn't so precise. I might have rotated the barrel beyond this point (maybe while shooting these pictures) can it be related?
cheers
Assaf

 

[Assaf]

BTW, how easy are these lenses to fix/CLA?
I heard that J9 for example, is almost impossible to fix. Is it the case here also?

 

[former member]

Some instructions are here:

http://www.ziforums.com/showthread.php?t=97

and Here:

http://pentax-manuals.com/repairs.htm

Collimating it is not so hard. Looking at your pictures, the focus looks like it is too "curved", ie not flat across the image. If that is true, it is more difficult to correct. I had two lenses that did that- I had to polish down the optics mount and move the rear module in slightly closer to the front.

First, try collimating it -adjusting the spacing to the film- and shoot a test roll of something flat. I use the planks from a wooden fence.

 

[Assaf]

Thanks, Brian, you've been most helpful.
If it's so, I can ask "my" technician to have a look.
Though, I don't know if it doesn't worth it returning the lens and looking for another one in a better condition. I have to think about it
cheers
Assaf

 

[former member]

If it helps, I've put up some photos from several J-3's, ranging from the best I've used to the "not as good". Most shots are wide-open or at F4.

http://www.ziforums.com/album.php?albumid=97

You lens is giving performance of one that I made from spare German and Russian parts. I still need to adjust the optics in it. It does well at F4, but wide-open remonds me of what you are getting.