[Leica] Are Leica lenses muliticoated?

[freakscene at weirdness.com (Marty Deveney)]

>Your interest in this question and the lengths you have gone to answer it 
>are refreshing.  And your assessment of the importance of multicoating to 
>the pictures we take seems to be justified.   Thank you for taking my 
>question seriously, and answering it.

You're welcome.  Years ago I worked alongside some microscopy experts who 
were working on a project to determine why window panes kept falling out of 
a tall building in the city where I lived.  The first hurdle was to work out 
the intricacies of cutting sections of glass to examine them using electron 
microscopy.  When looking for a sample I asked them if a lens element would 
do and they thought it was a fine place to start.  So they got started on a 
shattered Leica M 35/2.

>So, until recently, lens were liable to being scratched from aggressive 
>cleaning, but the hard coatings of today will not be scratched by excessive 
>cleaning?   Is that right?

Unfortunately, no.  Poor cleaning will scratch any lens, but what 
constitutes poor has changed.  Lens coatings have become harder 
incrementally.  Most coatings after 1985 or so are harder than the glass 
that they cover, but you can still scratch them with over enthusiastic 
cleaning.  One thing to watch out for is to remove large particulate 
material from the lens before polishing the surface.  I photographed some 
mineral sands processing sites years ago and got zircon dust on several 
lenses - the Leica ones were okay but some older Nikkors were really 
scratched up.  Lenses of today are less easily scratched than older lenses, 
but they will still scratch if they are cleaned inappropriately.

>Do you have any idea how recent these harder coatings are?

The changes in hardness were incremental, but from experience I find that I 
need to be a lot more careful with anything made before 1985 than after.  It 
varies between manufacturers, with the single coating applied to old Leica 
lenses (before 1970) among the softest coatings and the newest ones (after 
1990) among the very hardest.  I am still interested to know how many 
upgrades in coating technology Leica have applied since, say, 1980, and find 
it amazing that almost every other high-end lens manyfacturer makes a point 
of promoting their coatings while Leica does not.  They do, of course, tell 
us that many of their lenses have aspherical elements (while, for instance, 
Pentax do not) and call several of them 'APO' which, strictly speaking, 
means "these are well enough corrected across a wide enough range of the 
spectrum for us at Leica to call them APO".  Coatings interest me, 'APO' 
does not so much.

>And I have a question about this comment of yours: "One confounding fact is 
>that multi-coating is easy to retro-fit, so I am assuming out 35/2 was 
>multicoated when made, not later on."    Did you mean to say, not easy to 
>retrofit?

I meant it as I wrote it.  Providing that a lens has no aspherical surfaces 
and no scratches that go deep enough to scratch the glass, polishing and 
re-coating is a relatively straightforward undertaking.  I am not 
undermining the skills of John van Stelten and others who offer this service 
by any means - it is not something that an inexperienced or untrained person 
can just _do_ but I do know that an engineer with appropriate skills and 
experience can do it.  What I mean is that it is absolutely possible to 
multi-coat a lens that was not previously multicoated.  There was no sign 
that this was the case with the lens that we looked at, but I am not sure we 
would have known what to look for to check.  On the balance of 
probabilities, it seems more likely that it was multicoated by Leica when it 
was made, but the evidence to support this is on weight of evidence, not any 
empirical fact that says Leica definitely multicoated it.

I've seen a 50/2 rigid Summicron that was multicoated recently and it is 
amazing to see the difference it made when compared to its previous 
scratched state.

I hope this helps,

Marty


Gallery: http://gallery.leica-users.org/v/freakscene


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