Nikkor 50/2 LTM lens hack possible?

I won an auction for a collapsible
Nikkor 50/2 in LTM -- the mount
is in good condition but the front
lens element is scratched. Does
anyone know if it would be possible
to replace the front element with
one from a rigid Nikkor 50/2? If
so, I assume it would need to be
collimated -- any suggestions as
to who might be willing to under-
take the effort?

How badly is the lens scratched? It may lower contrast, but not be apparent in the final photographs.

I've taken the front block off of my 1948 collapsible to clean the hazed elements on each side of the aperture, as well as a few rigid lenses.

The front lens group -the first element and the cemented triplet behind it- comes out as a module, exposing the aperture blades. The construction of this front group changed early in the production, and I'm not sure how many times. Between the early production Rigid lenses in the 61 block and 62 block, the change took place and the front modules are not compatible.

SO: you need to find another collapsible, very early Rigid in the 50' block or maybe the '61 block. I'll try to find the close-ups that I've taken of the 61 and 62 block difference. "To the eye", the 1948 lens and 61 block look close.

How bad is the damage to the front element? Cleaning marks and even light scratches will not cause problems, especially if a hood is used. A gouge or heavy scratch can be bad news. Post some close-ups of the front element if you can.

- Brian

Brian, thanks for the reply -- I was
hoping you'd speak up on this one.

Do the lenses simply drop in? Or
does the swap require collimation
afterward? I'm wondering if this
is a simple DIY or if I need to send
the lenses out to someone else.

Sanders

As you might guess, I've already tried this with my spare-part 61 block front module going into Roland's 62 block lens. The 62 block lens was very scuffed up and had a flare issue. Nikon changed the mechanics of the mount and the front block fixture. I suspect the method that they used to control the stand-off of the front group to the rear group to get the focal length correct was changed. The 61 block front group screwed into place, but the lens could not be collimated. The front/rear spacing was too far off.

The 61 block "will probably" work in the collapsible. Depends on whether Nikon changed to mechanics more than once.

If your front group is really bad and the lens "blown", it is worth a try. My spare front is not perfect, but better than many.

Now: the collapsible Nikkor is a cool novelty in the LTM world. The optics are first-rate, it is hard-coated, and my 1948 lens is every bit as good as the "near-mint" late run black-rim 5cm F2 that I have. BUT: the locking mechanism is not as good as a Leica or Contax. It's easy to see why Nikon replaced the collapsible design with the Rigid lens so early in the production.