[Leica] Never clean a lens. Lens coatings.

[Jim Brick <jim@brick.org>]

Robert (delia),

Please be aware that there are a lot of folks here that have decades of
true photographic and Leica experience. Also be aware the all of these
subjects have been discussed, ad nauseam, before. There is, indeed, a
reasonable consensus among LUGgers. There are personal preferences, but
most people understand the technology that they are dealing with. My way of
talking, is simply my way of getting your attention so you won't pass it off.

I want you to think about something. Why, do you suppose, Leica (and other
major manufacturers) have spent millions of dollars developing coatings for
their lenses. Specifically, the front element of their lenses. All of the
air-to-glass surfaces in a modern lens has a coating. But only the outside
of the front element has the super duper very expensive multi layered
coating. Why is this??? I'll tell you. That's the first coating to get hit
with RAW light, from the outside world. Flare control and reflection
inhibition is needed MOST here. Raw bright light, reflective objects,
direct sun rays, high contrast areas, will produce flare, when hitting any
glass surface that doesn't have a really really good inhibiting coating on
it. The lens formula and the glass formula will have some bearing on this
as well. Anyway, if the light makes it through the front surface of the
front element in relatively good shape, it's on its way to making a clean
image. The coatings on the internal and rear lens elements are to suppress
reflections within the lens itself.

So, what have I just said? I have said that the first piece of glass that
the image forming light rays hits, must have the best coating. Anything
less than the *best* coating, and the light reaching your film will be less
than it could have been. There will be a level of flare above what it would
have been. You can also get double images (visible on large enlargements or
through a good loupe). Leica warns about all this on their web site.

So... is your Leica lens front element, very expensive, heavily researched,
very hard coating doing its job???

No. It's hiding behind two air-to-glass surfaces that don't have coatings
that even approach that which is on a Leica lens. So what do you suppose is
the result of this? I'll let you figure this out.

From what you have said to the group, you don't need a good clean coating
on your lens. You don't use it.

Jim


At 09:15 PM 11/23/98 +0000, Robert wrote:
>
>
>Jim and Ted,
>
>Pardon me for answering someone's question, next time remind me to run it
>first by you guys to see if its OK or not.  As I said, I didn't expect most
>of you to agree.
>My personal experiences simply differ from yours. As for it being " bad
>information" you may say all you want about the hardness of a lens MC, but
>as I pointed out, it only takes some cheap lens cleaning tissue to scratch
>it.
>And as far as your Leica lenses performing  better now than they did 22
>years ago,  I imagine that you know that the cause is most likely due to
>advances in film emulsions, etc.
>Why don't you two check Shutterbug, to see how many lenses are listed with
>cleaning marks and scratches, you won't find better proof.  End of
>discussion.
>
>Have a nice day,
>Robert
>
>"If you're an enemy, stay away.  I am not a nice man.  I will go to the
>wall for friends, but if you mess with me, I'm going after you"
>                                                                           
>                                               Jim Marshall             
>