The more I read about the lens fog issue (90TE, 50'CON), more I worry I am not care my lens good enough and lead those gem to fog. Is any one out there can suggest a good way to clean and keep the lens in the best condition? Should any kind of lens cleaning fuild and what kind of papaer for use to clean it? I did kept those lens in the humity controlled cabinet for storage. isn't it good enough?

Thanks all you out there.

-- joseph (jose_phla@hotmail.com), May 02, 2002

Answers

You are confusing 3 different issues.

The "fog" issue: involves a milky/cloudy haze on *internal* elements which develops over decades on older lenses. Mostly it can be cleaned, but requires dissassembling the lens which should be left to a professional Leica lens repairman.

The "90TE" issue: involves an *internal* deterioration of the rear lens group which is cemented into the mount and is not economical to repair. If you find a 90TE and it is still ok, it will stay that way at least in terms of the "90TE disease". If it has the problem (visible by shining a flashlight through the ends and looking for obvious signs of mottling, not just the odd dust speck) the lens is hopeless.

The "50 Cron" issue: involves soft coating on the front element which suffers from spontaneous breakdown as well as susceptibility to wipe marks with even the most careful cleaning. If you find a lens which has no or very few coating marks, put a UV filter on it and leave it there and hope the coating won't break down more on its own. If the lens already has bad coating, it can be re-coated. If the lens is otherwise mint, this might be an option to consider; otherwise you can get a later 50 Cron for less money.

As to general advice for cleaning Leica lenses, my personal advice is: less is more. I make sure my lenses are clean when I buy them, or at worst I carefully use a well-washed clean soft 100% cotton cloth and ROR. Then I put on a B+W MRC UV filter and leave it there until the day I sell the lens.

OTOH, if you believe the I-never-use-a-UV-Leica's-coatings-are- specially-hard-and-can't-be-scratched people, grab a handful of steel wool and a can of Comet and go to town ;>)

-- Jay (infinitydt@aol.com), May 02, 2002.

See also the entry on cleaning lenses in the Leica FAQ I maintain at: nemeng.com/leica/ 020e.shtml

-- Andrew Nemeth (azn@nemeng.com), May 02, 2002.

Joseph, If you are worried about getting your lenses dirty and cleaning them, best solution is to put a decent quality filter on the front, Leica B&W and Heliopan are decent choices. Whether or not these affect image quality is subjective.

-- Karl Yik (karl.yik@dk.com), May 03, 2002.