8mm Forum: Lenses which cannot be cleaned...

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Posted by Simon McConway (Member # 219) on February 22, 2007, 05:54 PM:

I have two or three lenses for projectors which look cloudy when held up to the light. Once dismantled, each individual glass element can then be cleaned. Even when cleaned and polished with Brasso (slightly abrasive)this "bloom/cloudiness" cannot be removed. It looks like the damage is actually within the glass, or where the pieces of glass are sandwiched together, looks like it's got in there. Any advice?

Posted by Oskar Jalink (Member # 667) on February 23, 2007, 07:44 AM:

The non-removability of the cloudiness makes me think it's a sort of lens-coating that has worn of. I've visited an optician once when I had a simular problem with one of my photocamera lenses. They had the equipment to clean the lens thoroughly.

Posted by Kevin Faulkner (Member # 6) on February 23, 2007, 05:57 PM:

Brasso....Blimey!

Some of the Elmo 1.1 lenses have suffered from this and I believe it's caused by the glue which is used to sandwich the elements together attacking the coating on the elements.

I have to say that I have in the past stripped Elmo lenses and cleaned them with optical lens solution with complete success so it may be another problem with the lenses in question. Maybe they would have to have the coatings removed and then recoated.

Kev.

Posted by Paul Adsett (Member # 25) on February 23, 2007, 08:15 PM:

I have noticed cloudiness on my Elmo lenses, but so far it does not seem to affect picture quality, but logically you know it must. On the other hand, my Eumig lenses are all crystal clear, so apparently, in the 1980's, the Europeans had a better handle on lens manufacture than the Japanese. Any significant polishing of the lens surfaces will affect the coating thickness and even the lens curvature, both of which can result in loss of resolution and contrast.

Posted by David Kilderry (Member # 549) on February 24, 2007, 12:57 AM:

Yikes! Only use lens cleaner and lens tissue on any glass elements in a lens. You will ruin the glass and wipe the booming if you use anything else. Rosco make a good lens cleaner and lens tissue; only a few dollars each.

Lens repairs are only for the very skilled, it is almost impossible to repair them unless you are skilled in optics. As Kevin says some balsoms (product used to adhere lens elements) can go off over time.

Your problem sounds like fungus clouding to me however. Cloudiness will effect contrast long before it effects focus. When it starts to spot or form a fern like pattern it is reaching advanced stages.

There is no cure for lens fungus, even if cleaned it will come back.

Even today the Germans are known for quality lenses, not so much the Japanese. This is the case in 35mm cinemas with Schneider and Isco streets ahead of Sankor.

David

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