Rob Smith wrote:
>My OM 10 died recently so I replaced it with an OM1n.
>I am looking to buy a more usefull 35-70 f4 lens to use.
>
Are you only loking at the f4? The f3.6 is generally regarded as the
better lens, although by now, past history and condition are also
factors. The 3.5-4.5 (NOT the 3.5-4.8), is much the same quality
optically, but amazingly smal and light. A cool lens.
>There are several for sale at varying prices depending on condition.
>What is, and causes fungal growth?
>
Well, obviously, it is a fungus. Since there are always spores around,
the problem is conditions in which they can grow. The conditions are
appropriate conditions of warmth and humidity.I believe more specifics
are in the archives. I know solutions to prevent fungus are there.
>Does it affect picture quality?
>
Depends on how much fungus, but it certainly can, and often does.
>Can it be cleaned?
>
There are lots of different species with different characteristics.
Generally, mild cases can be cleaned, but some eat away the lens
coatings and I"ve heard claims that some actually etch the lens surface.
In either case, repair is uneconomic or impossible.
>Can lenses be dismantled cleaned and put back together or are there
>adjustments inside requiring specialised equipment?
>
With most of the garden variety lenses, disassembly and reassembly is
possible for the mechanically competent with a few tools many people
don't have. However, zooms are more complicated and some downright
diabolical. The 35-70/3.6, for example, has something like 100 loose
ball bearings that fall out if you open it wrong.
>Does anyone have any information on doing this?
>
Yes. Don't buy a lens with fungus. It simply isn't worth it except as
entertainment with no expectation of ending up with something usable.
Some of us have purposely bought lenses with fungus or other problems
just to take apart and learn from at low economic cost. Otherwise, the
difference in cost between a lens with fungus and one without is less
than the risk of the cost of a cure. Only if the lens in question can be
taken for an estimate from a qualified repairperson beforehand would I
purchase it for later actual use. I don know of one case where a dust
pattern was mistaken for fungus, and the repairer cleared up the difference.
Moose
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