Re: FINGER PRINT ON LENS

[Amilcar de Oliveira <amilcar@domain.com.br>]

jsaravia@zeus.uniandes.edu.co wrote:
> =

> Last Saturday the son of a close friend of mine, put his little finger =
on
> the back element of my 35 Summilux AHSP, when I realized that I tried t=
o
> remove it with a dry microfiber cloth (according to  the Leica
> instructions), but what happened was that the print wasn=B4t cleaned at=
 all,
> instead, the dirt was all over the back lens, since this is the first t=
ime
> it happens to me,  I decided leaving it like that and ask for advice
> -----------------------------------------------------------------------=
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> -----------------------------------------------------------------
> =

> Thanks in advance,
> =

> Jorge Saravia

Jorge, however hard the coating is, it's very thin, so don't trust it as
a protection. The best cleaner I found is 70% sulphuric ether / 30%
ethylic alcohol. I tried Xylol (used by microscopists), isopropyl
alcohol and methyl alcohol, all lab grade, but they leave too much
residue and require a lot of applications to get a good cleaning. Wash
the microfiber cloth with detergent and touch it on one  side only, the
one that won't touch the lens. It's very easy to contaminate the cloth!
Apply the cleaner with lens cleaning paper just barely wet (don't soak
it, just touch quickly the surface of the liquid with the paper) and
wipe with very little pressure in a **continuous** spiral from the
outside to the center. Move the lens so you can see by reflection the
tracks your wiping is making, and care that they overlap. The dirt will
accumulate in the center of the lens. Wipe it off with the paper.
Breathe on the lens and wipe the last spot off with the microfiber
cloth. If you still haven't got all dirt off, it's better to repeat from
the start. To get a really good cleaning, you have to be conscious of
what you're touching, wether it's contaminated and wheter it's going to
end up on the lens.
I hope it helps,
Amilcar