Nikon 8mm 2.8 fisheye- spare parts

[Erik Lund]

Yes, an approach could be to use the windscreen chip repair glue.
Blackening them out will make them even more visible in the images, also in the out of focus areas.

[Birna Rørslett]

Roland's suggestion of using a glass "filler" to repair the cracks in the rear element sounds appealing. What is there to lose any way with a lens this degree of damaged? Might work well in particular if the lens is not stopped down too far.

[MEPER]

The windscreen repair people are very keen of that a tape is put over the crack just after the accident to be able to repair the crack with a good result.
Therefor I think it will be good to clean the cracks in the rear lens element very carefully before "filler" is put in.

For the DIY kit you can get there is a sharp blade to cut away excess resin. A similar kind of method on a curved surface is probably necessary and then a kind of polish that may not destroy the coating or if it does the lens will probably work anyway. Special polish for vinyl / plastic / plexiglass exists.

[schmuku]

Have you tried the lens stopped down to see how bad it is?
Could the rear lens be grinded/polished?    ….you will loose coating and change the optical formular a bit but maybe it will work but has to be done by an expert that has the equipment (proper grinding/polish tools).

In old days a scratch could be "repaired" by putting black paint into it so it would not cause "artifacts" by reflected light in the scratch. But the damage you have to the lens is not just a scratch.
Repairing of the lens element same way as you would repair a "stone on windscreen" of a car could also be something to try.

The best solution is a donor lens?

A donor lens could be hard to find due to its rarity . I found a repair manual, now ill try to fix the carousel and than take a couple of test shots. I could sell it as spare part donor lens but i would rather try to fix it.... I asked  a specialist firm and they said they could build a new lens from scratch but that would be around 3k Euro.  I will contact some more and ask if some firm is able to fix it. Does anyone know some firms in Europe?

[schmuku]

The cracks go deep into the lens, you cannot polish or grind them out without ruining the lens.

Minor chips and cracks in a car windscreen can be repaired with liquid fillers (resin?). This removes the air from the cracks which cause reflections, they become nearly invisible. I wonder if the same could be used to repair the chipped lens? The optical properties (refractive index, dispersion) of the material filling the crack will be different from the glass so it won't be as good as a replacement lens, but it should be better than nothing. The chips are small relative to the entire surface, I think if done right it could be successful.

It might depend on whether they are clean cracks into the lens (should be easy to repair), or chips from the surface (may be more difficult), it is hard to say from the picture. I wonder what the lens doctors here think of this suggestion, worth a try?

It is worth a try but i will do some more researche first. The surface is flat and the are no chips missing from the lens.  Does anyone know a company that is specialised in repairs like that? I think just filling it up with liquid glas for cars by myself will do more harm than good. But thanks for the input!!

[schmuku]

Roland's suggestion of using a glass "filler" to repair the cracks in the rear element sounds appealing. What is there to lose any way with a lens this degree of damaged? Might work well in particular if the lens is not stopped down too far.

I will look more into that, could be a possible "fix", Thanks a lot for your comments. Has anyone ever did a repair like that before? Is there a product that can be recommendet for that kind of repairs? There is not too much information regarding this topic on the internet. I am happy for every bit of information or source. Could the glue, that is used to glue lens groups together be an alternative?  Maybe i will take an old broken lens and try it before doing it on the "real" lens.

[Birna Rørslett]

Glue for cementing lens elements likely won't work as well. It has a different purpose. A quick 'net search for car screen repair kits should bring the answers you require.

A word of warning: if possible, do *not* remove the entire rear group when you repair the lens. Tolerances are very small and the lens might require realignment in a collimator.

[Roland Vink]

Before using the glass filler on your lens, I would recommend experimenting by repairing a chipped UV filter or similar. If necessary you could even purposely damage a cheap filter if you don't have anything with similar chips. Once you are confident with your technique and end result, then try it on your lens.

[schmuku]

What about "Canadian Balsam" ? That stuff is reversible and is used to cement lens groups...

[Birna Rørslett]

It might be too soft. Do remember the need for the occasional cleaning of the rear surface. At the very least, do a test with a broken filter or similar to learn how the repair stands up to cleaning.

[Erik Lund]

The windscreen repair people are very keen of that a tape is put over the crack just after the accident to be able to repair the crack with a good result.
Therefor I think it will be good to clean the cracks in the rear lens element very carefully before "filler" is put in.
...

I would suggest the opposite!

A windscreen is exposed to all the debris from traffic and what else is flying around it drives through.

A lens sitting on a camera or with a with a cover is more or less completely free of that.

If you put anything on it first it will be sucked down into the cracks.

[Erik Lund]

Glue for cementing lens elements likely won't work as well. It has a different purpose. A quick 'net search for car screen repair kits should bring the answers you require.

A word of warning: if possible, do *not* remove the entire rear group when you repair the lens. Tolerances are very small and the lens might require realignment in a collimator.

I completely agree.
Also, Canada balsam is not for these kinds of repair

[schmuku]

I am gonna buy that windscreen stuff and try it on an old damaged filter. After that i will see what to do. i will keep you updated. thanks for all the help !

[Birna Rørslett]

In any case you are secured an impressive book shelf support

[pluton]

I am gonna buy that windscreen stuff and try it on an old damaged filter. After that i will see what to do. i will keep you updated. thanks for all the help !

Keep alert for another copy where the front of the lens has been destroyed but the rear has survived.  I know it's not likely, but it is possible.