I can only repeat what I said earlier, based on my current ownership of 5 prewar f3.5 Elmars, 2 Summars and 3 Summicrons (different vintages). I have also owned 2 or 3 Summitars in the past.
Originally Posted by Nicholas Lindan
Nuimerous examples of the above exhibited haze on internal surfaces, which was cleaned off at reasonable cost by my usual repair service, Newton Ellis of Liverpool, and has not returned. If any lens is left in a dirty state for too long, the haze may attack the glass and cause pitting, which can be dealt with only by a major stripdown (separating lens groups), regrinding, repolishing and recoating. This will almost always not be cost-effective.
However, the only Leica lens with which I have experienced this problem on a systematic basis is the f2.8 50 mm Elmar, which, as I said, has its iris diaphragm located immediately behind its first element instead of between elements 2 and 3 as is usual with Tessars. The fogging I have experienced with these lenses I attribute to vapors from the iris lubricant - the fogging seems to be promoted by storage of the lenses on a camera which is lying down with the lens facing upward. Both the examples of the f2.8 50 mm Elmar which I acquired (as part of job lots) were pitted so badly that I simply had to throw the lenses away. I have not experienced this problem anything like as badly with Summicrons of a similar vintage or even Summitars, which are older.
I have had a problem with mold with 135 mm Hektors - since these are available cheaply, I chose to discard a couple of poor examples and look for better ones rather than consider repair. The only Leitz lens which suffers from serious glass deterioration as far as I know is the f2 Summar. This lens is also often found in poor condition because the glass is soft and does not withstand cleaning.
In short, I wouild say avoid 50 mm f2.8 Elmars - major risk of problems. There is no reason to avoid 1950s Summicrons, these may need at most a straightforward clean and have lower contrast than their modern equivalents, which gives interesting results particularly with color. The modern Summicron-Ms seem to have been recomputed in the days before high-saturation color film so that amateurs could blow their friends' socks off at the camera club with the "superior" quality (higher micro-contrast) of their pictures - with b+w, the contrast of a modern Summicron needs a lot of taming with extra exposure and reduced development.
I agree with Nicholas fully.
One thing I would like to add: when you buy a used lens you don't know its history.
Leitz has been using the highest quality greases and lubricants over the years, expensive stuff, verry expensive and verry good.
If a lens needed a grease-change due to sand/grit and that was done by an independant repairman that didn't use the propper grease, you
will have a problem sooner or later.
Yes, but ...
Originally Posted by archphoto
a) Grease needs to be replaced as part of normal servicing, not usually because of sand or grit but because it hardens and dries out with time. The service interval could be anything from once every 5 years for a professionally-used camera to once every 40 to 50 years for a camera subject to light amateur use.
b) Independent repairmen (at least the ones I use) do use the right materials! The difference in cost between the cheapest and most expensive grease in the quantity needed for one lens is TINY!
If you buy a lens on e-bay or elsewhere, you will of course ask the seller whether the diaphragm is working smoothly. If it is, no problem - if it isn't you either factor it the cost of servicing or find another lens. The whole point I am making is that 1950s Leitz lenses can be perfectly usable and offer picture-making possiblities that other lenses don't!