Leica LTM What is haze?

[Dralowid]

T
When you encounter a non curable case of haze (not removable by wiping the element with the usual solvents/cleaning fluids) this usually means that the chemical structure of the glass at least at the surface of the lens has been permanently changed and damaged. The changed chemical structure will lead to a change in optical properties. Such a lens is not repairable (unless you repolish and recoat the lens element at great cost and with questionable effects on the optical properties), the elements will have to be replaced.

If you find yourself with an old uncoated lens or a cheap coated one with significant haze there is nothing to be lost. It is surprising what can be achieved with care. Using the finest jeweller's rouge or equivalent, and a lot of patience it may be possible to polish the lens surfaces to a point where they at least appear clear. This is quite easy on old lenses with 'softer' glass. Obviously any coating on a coated lens will have gone.

As to performance after such treatment? Not sure what to say but I have a coated Summarit one of whose elements I've polished and the coating lost. It is noticeably better than it was before the treatment. I've also done this on an old uncoated 90mm Elmar that you could barely see through that is now really quite good.

Think twice before you start though, age has made many of these lenses difficult to open without tools slipping etc etc.

 

[David Hughes]

Hi,

About lubricants vaporising; I don't think it unproven that heat causes liquids and semi liquids to vaporise. But I do think that over the years each maker will have tried different lubricants and so there is no one golden rule for all lenses.

So really it depends on when the lens was made, cleaned and re-lubricated and the lubrications used. Meaning a lot of variation and no simple fits-all answer. Especially when we could be talking of a time span of, perhaps, hundreds of years...

Regards, David

 

[pyeh]

Joeswe and Dralowid, I sent these two lenses to a well regarded repair shop on the other side of the continent from me (Sydney to Perth) and the diagnosis was that the haze could not be completely cleaned off. With the Summicron, they thought they might be able to do it if they removed the costing first. I was prepared to sacrifice coating and authorised the work. They tried it first to a small portion at the edge of one element as a test, and then tried to remove the haze but couldn't, so stopped. I now have a dust free, hazy lens with this unsightly patch of missing coating on one element deep inside. I almost cried.
However, when I used it, as well as the Summilux-with-haze, they both seemed to give perfectly acceptable images, as they did before, so I've stopped fretting. I don't stress test them against the light though. I'm sure I'd be disappointed if I did.

 

[sevo]

Hi,

About lubricants vaporising; I don't think it unproven that heat causes liquids and semi liquids to vaporise.

All the camera and watchmakers greases I own are specified to vaporize somewhere above 200°C - way beyond the point where every plastics part in a lens will have molten down. Usually, grease on inner surfaces will be due to creep, not evaporation and condensation.

 

[David Hughes]

All the camera and watchmakers greases I own are specified to vaporize somewhere above 200°C - way beyond the point where every plastics part in a lens will have molten down. Usually, grease on inner surfaces will be due to creep, not evaporation and condensation.

Hi,

I agree but that's modern lubrications in modern/plastic cameras. Not old fashioned lubrications in old fashioned metal and glass cameras and lenses.

Modern lub's first appeared as I recall it in the 70's and probably a lot later on in the old USSR. Even when modern oils etc were being used not all cameras were sent back for an oil change and the modern lub's would not go in until the first service or repair, perhaps. I know some who swear by old fashioned ways and won't change. Or worse, mix their own concoctions...

And some of the "modern" ones were a little iffy with all sorts of strange and volatile bases (like lighter fuel) to get the lubrication where it was needed. And temperature is not the only cause of vaporisation.

Anyway, I think we'll have to agree to differ over this because there's so many variations to it.

Regards, David

 

[Dralowid]

For what it is worth I have found that later 50 mm Elmars can have haze or a film of something next to the aperture blades and earlier ones are much less likely to be so afflicted.

I had a poor collapsable Summicron once that would cloud over and clear (almost) whenever it felt like it. The results on clear days weren't too bad. The mount was in such bad shape that it wasn't worth the effort and I sold it (correctly described!).