Isco Kiptaron 1.8/75 repair

[alex ph]

I've got a 16mm projection Kiptaron 1.8/75 with an idea to use it on APS-C without much of vignetting. Unfortunately when the lens came in a lot, the inner glass was rattling inside, making the lens unusable. When I unscrewed the rear glass to take the middle off, the front lens fall off too. Visibly, it was not fixed and was just in its destined place, "fixed" by a good fit of its shape to the barrel.

This way I discovered three glass elements which compose together something that looks pretty much like a triplet: a bold bi-convex front, an asymmetrical bi-concave middle and a convex rear.

#1


As the front and the rear glass have their fixed positions inside the barrel, the most problematic is the position of the mid element. And here I have no idea at which distance it was originally put into. Just because the barrel is straight inside, and the mid element shifts down freely until it touches the up surface of the washer retaining the rear element.

#2


Was there a spacer and someone took it off, or was the original composition fixed in another way, ot maybe there were four elements, and one more is missing together with the spacers? I am asking some help or hints, as I could not find an available optical scheme which could answer to this question.

To test different configurations myself, I put a very thin layer of adhesive on the side of the mid glass which let me temporarily (and not very strongly) fix the glass inside the barrel. Moving the glass inside, I tried various positions of it within the reassembled triplet. Nothing worked. At some point there is a very fuzzy image that does not recall by far an OK projection quality. But in many other positions (the mid element very close to the rear one or pretty much to the front) there is just "milk" on the screen. Paradoxically, the reversed lens gives a bit more of shapes than the lens directed correctly. But if I flip the mid element, this does not help either.

#3


So, my question is if someone has bits of documentation on Kiptarons or maybe practical knowledge how to repair the issue and reassemble the troublesome lens.

[calvin83]

IF the lens is Petzval type, take a look at there if you can't find further info.
http://forum.mflenses.com/roger-cicala-tests-lomographys-petzval-lens-t67138.html#1397448

[alex ph]

Thank you very much, Calvin! I'll study this thread. Even if I am a bit lost in specs: Kiptaron looks more a triplet than Petzval scheme. But I'll read more attentively.

[calvin83]

A triplet will have similar size elements. Typical fast etzval projection for 16mm film will have big front element and small rear element.

[alex ph]

Thank you for the clarification! Now is just to understand what to do with the third, rattling element.

[calvin83]

Someone who owns the lens should be able to check it for you if your lens is complete.

[alex ph]

Hope to get an owner's hint! Thanks again for your friendly attention.

[simple.joy]