Re-housing Cooke Panchro (pre-cleaning and scratch-fixes)

Petter Englund · January 21, 2017

Good evening everyone!

Looking to get a hold of a set of old Cooke Panchros to send in for re-housing at P+S in Germany or somewhere else where they do it!

In my attempt to get a hold of a set of old-housed Panchros in suitable condition -- how important is it that the lenses are in absolute perfect condition? Almost all older lenses show some sign of wear like fungus, oil on the aperture blades and/or dust inside.

Is that extremely critical or is it standard praxis that the re-housing tech firms clean the interior of the optics at the same time they do the re-housing?

If not, are fungus, oil on the aperture blades and dust on the inside something that can get fixed for a reasonable price? Any guidelines on price per lens?

What about cleaning marks or small scratches? I see a lot of advertisements about scratch-fixes etc. Can it be done in the first place and secondly, can it be done for a reasonable price?

I'm not looking to spend the same amount I buy the glass for in cleaning fees.

If that's what I should expect, I will go for another set of lenses.

Let me know if you have any experience on the matter!

Thank you!

Stuart Brereton · January 21, 2017

Rehousing the lens requires that the lens be completely disassembled, and most of the existing mechanical parts be discarded. Whatever is kept along with the glass would have to be cleaned and serviced, so dust and oil is unlikely to be a problem. Fungus, however, might be, as it may well have eaten into the lens coatings. Cleaning marks and scratches can be fixed by re-coating the front element. Whether or not that would affect the vintage Cooke look, i don't know.

I think True Lens Service in the UK are considered to be the best re-housing of Cooke Panchros.

Dom Jaeger · January 23, 2017

TLS conversions are superior, but more expensive, and last I checked they have a much longer waiting list than P&S.

Most lens issues can be resolved during a conversion, as Stuart mentioned. Light coating scratches or other coating damage including fungus etching can be removed by polishing and re-coating, but deeper scratches, pitting or chips can't really be fixed.

Fungus often occurs between doublets, which means splitting them to be able to polish and recoat, and then re-gluing, so it can become expensive.

The one thing I've found is that if a lens is optically poor (due to element decentration, swapped components between lenses or some other non-coating issue), a conversion generally won't make them better, because the original optical block is still used. So if possible start with a lens that performs well (something a lens tech can tell you quickly on a test projector).

Stuart Brereton · January 23, 2017

Dom, do you know how much of the original lens is retained in these conversions? Obviously the housing and focus helix is discarded, but do they keep the lens tube and iris assembly?

Dom Jaeger · January 23, 2017

Hi Stuart,

Yes in my experience they keep the original inner optical block and iris. It would be a very serious job to reconstruct all of the element housings, lock rings and iris assembly, another order of accuracy beyond just the outer housing and focus mechanism. Usually there is no need to rehouse the individual elements, since the optical qualities are what you want to keep, it's the mechanical aspects like barrel diameter, focus mechanics and markings, gear ring positions and mount that need updating.