Archived posting to the Leica Users Group, 1996/05/29

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Subject: Re: Lens cleaning
From: Tom Hodge <>
Date: Wed, 29 May 1996 15:56:01 -0400 (EDT)


I spoke to an old acquaintance still in the retail camera biz this past
weekend about the thread on lens cleaning here on the LUG and how someone
mentioned using highly refined petroleum spirits, cotton wadding and some
type of compressed air on lens surfaces.  He said he'd run it by his crack
maintenance man for comments.  And so...... 

1) The maintenance man said never use anything OTHER than an aqueous
solution to clean lens surfaces.  This includes some very specific
buffered alcohol solutions (aqueous-based) that make up many over-the-
counter camera lens cleaning solutions.  NO PETROLEUM SPIRITS OF ANY KIND! 
(At least not unless they're specifically intended for use on optical
elements.  I suspect they are few.  Alcohol-based, yes; petroleum-based,
I'd be very, VERY careful!)  They can attack the lens coatings.  All of you
"weekend warriors", put the lacquer thinner away! 

As far as a pressurized gas, the camera cleaning whiz said be very careful
when using anything in a can as the propellant alone could leave a residue
on the lens or attack delicate lens coatings.  (I think the newer freon or
fluorocarbon-free propellants are the least damaging.  T.H.) He said if
you can't blow it off with a good gust of breath or knock it off carefully
with a very soft camel hair brush made specifically for cleaning lenses
and so on, don't do it yourself. 

(I remember years ago a well-educated chap I worked with wanted to get
some dried water spots off the front element of a highly-specialized test
apparatus lens and used 'versine" or something like that - a very highly
refined petroleum spirit or distillate - and it ruined the lens.  Of
course, besides destroying the coating on the front of the lens, it also
ran down inside the optic, doing irreversible damage to the entire
assembly.  {See point 2, below.}  There went a thousand bucks down the

The over-the-counter lens cleaning solutions will remove water spots, he 
said.  Use a lens tissue wrapped on a cotton Q-tip and address each spot 

2) Of course, NEVER PUT any FLUIDS DIRECTLY on ANY lens surfaces!  NEVER! 
Always put the liquid on the cleaning medium, whatever it is. 

3) The cleaning wizard highly recommended the micro-fiber type cloths but
conceded they may not be the most absorbent materials for any cleaning
solutions.  They're for final smudge-free wiping after softly breathing on
the pre-cleaned lens surface.  He suggested good, high quality lens
cleaning tissues available at any camera store to apply any needed
solutions.  No handkerchiefs, no shirt tails, no diapers, no well-washed
cotton cloth - nothing that's not specifically designed for optical
cleaning.  And for God's sake, nothing commercial to clean windows (i.e.
"Windex"), silicone-treated eye glass tissues or anything like that. 
Cotton balls, cotton swabs - unless wrapped with a lens cleaning tissue -
or anything that could leave strings, lint or other fibers behind were
absolutely no-no's, too.

4) Do everything sparingly, gently and rarely.  The repeated circular
wiping and wiping can be terrible for a lens if not done correctly and the
delicate coating, he said.  BE CAREFUL!  If your lenses are getting that
dirty, that often, put a UV filter on them, he said.  Otherwise, watch
your practices and just keep the front element covered whenever possible. 

5) Basically, when in doubt, don't do it yourself.  That is, don't think
every lens cleaning problem is self-solved.  Take the seriously dirty lens
to a professional; they know all the tricks of the trade and can save a
front element if the owner hasn't already done it in.  The cleaning pro
says he doesn't want customer's money to clean a lens just for the sake of
money.  He simply wanted to see fewer lenses turned over to him he
couldn't do anything with because the owner had already screwed things up. 
He said most camera repairpersons are over-loaded with work as it is so he
certainly wasn't trying to drum up more business.  Besides, he added, lens
cleaning isn't all that profitable to him and he'd just as soon not do
those regularly.  He said he was more into the mechanical details of
cameras and such - as are most general repair shops - and lens cleaning
wasn't his bag.  He only preferred lost causes (impact damage, dropped in
water, misc liquids spilled on the lens, etc., etc.)

6) Finally, the cleaning whiz mentioned he's seeing a rash of damaged
reflex mirrors.  (No problems for us "M" freaks!) 

People, unless you haven't heard, the mirror on a single lens reflex (SLR)
camera isn't a conventional mirror you can clean.  The reflective
silvering (deposited via a vacuum coating process) is on the FRONT or top
side of the tiny glass plate - the side that actually reflects the image -
and isn't sealed or coated with anything.  If the silvering were on the
backside of the glass - "a la" a home mirror - you'd get a weird view as
the image then reflects off of the silvering underneath AND - to a lesser 
degree - the front surface of the glass:  You'd see a "ghost image." 


This is doubly the case if your camera has an interchangeable viewing 
screen and access to it is thru the mirror box area.  Be careful!! 

NEVER spray the mirror in an SLR with "canned air", either.  A residue -
one you can't clean off without damaging the mirror - can form on the

Don't even think about it! 

Any little dirt specks on the mirror will have no influence on the
pictures.  The silvering is so soft and so delicate, just wiping it
lightly with a camel hair brush will probably scratch it.  The scratching
will still have no affect on pictures but is terrible to view thru.  Only
solution:  Professional replacement. 
This may not be as critical on newer cameras with some technological
advancements in the silvering process and deposition but it's the 'touch
of death' to older SLR mirrors. 

These all seem like good, common sense rules but I'll bet most of us have
stepped over the lines more than once. 


Tom Hodge
Davidson, NC
(no where near Grant's Pass, OR)