Jupiter 3 question

[archive59]

I have recently acquired a Jupiter 3 f1.5/50mm lens (N6314391). I got it quite cheap so I wasn't expecting it to be perfect and the optics are very clear with only a single bubble in the rear element to spoil things (and I was aware of that before I bought it). The one problem, if it is a problem, is that the focussing scale does not line up. The mark is on 1 at the stop on minimum focus and at maximum focus the stop is about 10mm past infinity. After doing some simple tests it seems to me that the lens is focussing where it should do with reference to the rangefinder but obviously the distance scale and consequently the DoF are not usable. Is this correct? Is it a simple matter to disassemble a J-3 and rectify this problem? Any help would be gratefully received.

As an aside, I bought the lens attached to a Zorki 4 (1967 model) with the intention of disposing of the camera as I've always found the Zorki 4 a bit disappointing but this one seems quite nice and the shutter is considerably quieter than the other Zorki 4 I have lying around. And the J-3 does look pretty good on it.

Thanks,

Mark

 

[johannielscom]

Hi Mark,

Just cut a small paper sticker and copy the distance settings (correctly spaced!) on it. Stick it to the lens and you can at least use it without getting confused until you get it fixed.

You should Ask Brian Sweeney whether this is an easy DIY job. I haven't got a clue.

 

[Daan]

if i recall right, it's pretty easy to adjust the distance scale. Just put it on infinity unscrew the three screws and aline it to infinity. That should be it.

 

[archive59]

Hi Mark,

Just cut a small paper sticker and copy the distance settings (correctly spaced!) on it. Stick it to the lens and you can at least use it without getting confused until you get it fixed.

You should Ask Brian Sweeney whether this is an easy DIY job. I haven't got a clue.

Hi,

Thanks for that suggestion, it's a good one. Not sure why I didn't think of it.

 

[archive59]

if i recall right, it's pretty easy to adjust the distance scale. Just put it on infinity unscrew the three screws and aline it to infinity. That should be it.

If only it was that simple. I've just undone the three screws holding the ring with the scale in place but they have associated holes in the actual focussing mount into which they screw so I can't line up infinity. It was worth a try though.

 

[ZorkiKat]

I have recently acquired a Jupiter 3 f1.5/50mm lens (N6314391). I got it quite cheap so I wasn't expecting it to be perfect and the optics are very clear with only a single bubble in the rear element to spoil things (and I was aware of that before I bought it).

Mark

The bubble won't affect the quality of the picture. One tiny bubble is virtually invisible, in as far as the lens is concerned. Bubbles could be found even in other good quality lenses. They passed quality control because a tiny bubble or two, or even more, in the glass is considered insignificant.

Here is a translation about the bubbles found in Jupiter lenses, from an old FED instruction manual:

Preparation of special grades of optical glass presents significant technical difficulties. In particular it is difficult, and for some grades of glass it is impossible to get rid from air bubbles, formed in the mass of glass during smelting. Present methods of elimination of these bubbles in some grades of optical glass made by us or the foreign technical equipment of glassmaking for the present has notbeen achieved. For these reasons in lenses of complex (difficult) foreign and Soviet objectives always it is possible to notice a quantity of bubbles. In itself bubbles practically do not influence quality of objectives and sharpness of pictures, and, hence, objectives with bubbles on lenses at all are not defective.

 

[brachal]

"Quote:
Preparation of special grades of optical glass presents significant technical difficulties. In particular it is difficult, and for some grades of glass it is impossible to get rid from air bubbles, formed in the mass of glass during smelting. Present methods of elimination of these bubbles in some grades of optical glass made by us or the foreign technical equipment of glassmaking for the present has notbeen achieved. For these reasons in lenses of complex (difficult) foreign and Soviet objectives always it is possible to notice a quantity of bubbles. In itself bubbles practically do not influence quality of objectives and sharpness of pictures, and, hence, objectives with bubbles on lenses at all are not defective."

My 1951 Leica Manual says pretty much the same thing.

archive59, have you looked at the J-3 link here?
http://pentax-manuals.com/repairs.htm