[Leica] Are Leica lenses muliticoated?

[robertmeier at usjet.net (Robert Meier)]

Marty,

Thanks very much.

Bob



> >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
>
>
> -- 
> Be Yourself @ mail.com!
> Choose From 200+ Email Addresses
> Get a Free Account at www.mail.com
>
>
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information