My 50mm lens does have some scratches on it. I have been told-by my boyfriend-that glass is harded than steel (he's a gearhead engineering student not a Leica gear hound yet), and the coatings are metal compounds. how could a lens ever be scratched with lens paper or cloths? Glass is made of sand (quartz) after all which is harder than steel. how can ordinary dust being cleaned off a lens scratch it?

-- Allison Reese (a_b_reese3@hotmail.com), April 24, 2002

Answers

Generally, you get something like that same quartz sand, and you use a cloth to wipe it off- only you grind it into the face of the glass instead of push behind or blow it off. So now you have a sharp, irregular grain of this same really hard stuff scraping into the face of the coating and the glass. Simple physics and dumb luck. A few light scratches in the coating, while they won't help- especially with value- but they won't really ruin the ability of the lens to help you take a good photo.

BTW- I like the YET about your boyfriend not being a Leica gearhound...

-- drew (swordfisher@hotmail.com), April 24, 2002.

I'm not sure that the relative hardness of the pure materials is really the issue here. If the "scratch" on the front surface of the lens is actually just a microscopic removal of the coating, the underlying surface of the lens itself may not be scratched. The effect on image sharpness, however, would still be the same, I'd think. Thus, it might make more sense to think of the fibers of the tissue goughing or plowing up the coating, separating it from the surface of the glass, as opposed to scratching either the metallic coating or the underlying glass.

-- Ralph Barker (rbarker@pacbell.net), April 24, 2002.

Metals may be hard - metal compounds don't have to be. E.g. soft squashy talcum powder, which is magnesium silicate (2 metals plus oxygen).

"Hardness" has to do with the strength of the atomic bonds between molecules, not the makeup of the molecules themselves. "Rust" is an iron compound with weak bonds - Chromium steel is an iron compound with strong bonds.

Glass varies - some is very hard and some is very soft.

As to how a cloth can scratch anything - it ain't the cloth, it's the little bits of dust trapped in the fibers and between the fibers. Some of which will be quite hard fragments of powdered sand, and at least as hard as the glass (since it's the same stuff - a silicon oxide).

Ain't physical chemistry fun?

-- Andy Piper (apidens@denver.infi.net), April 24, 2002.

Allison:

To add to your confusion, look at an old piece of glass or mirror in excess of 100 years old. It will be thicker at the bottom than the top, and if you look at it closely from an angle, you can see imperfections in the object viewed. Glass flows over time, at least the older stuff does. Hard, that is a relative term.

Cheers.

-- Mark J. (logical1@catholic.org), April 24, 2002.

Allison,

I have to agree with the last post as glass is more in a liqid state than a solid state. Minor scratches and/or coating marks on the front element will probably not affect image quality. It would be worse if on the rear element. Also, having been a boyfriend on several occasions, we tend to act like we know what we're talking about even when we don't.....

F. William Baker

-- F. William Baker (atelfwb@aol.com), April 24, 2002.

I personally scratched (or, being more exact, ruined lens coatings) coated lenses on my binoculars while simply wiping the fog off them. No dust whatsoever, just clean gloves and a clean lens covered with fog! The lenses look now like they have a "hole" in them, but the binoculars still function fine.

-- Eugene Scherba (smallglove@icqmail.com), April 24, 2002.

RE "glass flowing": A reality check.

But this idea HAS been around for forever - when my Dad showed me around the cathedrals of Europe in the '60s we carefully looked for (and found) the "flowing" glass.

-- Andy Piper (apidens@denver.infi.net), April 24, 2002.

Ive read that Leica test their lenses by rubbing them continuously for god knows how many minutes with an eraser that contains pumice stone fragments amongst other nasty things and they claim that no visible damage can be seen afterwards. Personally I have not verified if this is true!

If you are prone to scratch your lens glass, id stick a uv filter on the front.

-- Karl Yik (karl.yik@dk.com), April 25, 2002.

i almost flunked college chemistry.

-- Dexter Legaspi (dalegaspi@hotmail.com), April 25, 2002.

Ive read that Leica test their lenses by rubbing them continuously for god knows how many minutes with an eraser that contains pumice stone fragments amongst other nasty things and they claim that no visible damage can be seen afterwards. Personally I have not verified if this is true!

I used Nikkors for 10 years before switching to Leicas and just though normal cleaning I damaged the coating on at least one of my lenses. Leica coatings, at least for the last 35 years or so, are much harder than the coatings on the old Nikkors. My oldest Leica-R lens is at least 25 years old, I've cleaned it as needed, much as I kept the Nikkors clean, and there are still no signs of damage to the coatings.

-- Douglas Herr (telyt@earthlink.net), April 25, 2002.

In my experience Leica coatings are far from invulnerable. Before I began protecting all my lenses with UV filters I ruined the front element of a 180/3.4 APO-Telyt-R (a 2-element cemented group costing $800 + labor to replace)by breathing & wiping gently with a microfiber cloth after first using a blower brush. There was evidently one grain of sand left behind and it made mincemeat out of the coating. Anyone who wants to believe Leica coatings are somehow un-scratchable even with normal care, let alone wanton scrubbing, is welcome to their belief. They evidently mentally block out all the ads for Leica lenses with "wipe marks" or "cleaning marks" at deep- discount prices. But newcomers who have just plunked down hard- earned money should recognize that the Leica-coatings-are-stronger myth is just that.

-- Jay (infinitydt@aol.com), April 25, 2002.

Allison. Most "scratches" on relatively modern lenses are really hairline marks on the coating made from too vigorous or improper cleaning technique. Of course, applied to excess, it is possible for the scratch to etch the glass. While we're on the subject, some older Leitz lenses (eg., Summars, which were made from 1932-1939 and were not originally coated) have relatively "soft" glass; and these lenses nearly always show up with hairline marks from cleaning on the outside glass surfaces.

Early Leitz coatings [late 1940s-1950s (eg., as found in 50/1.5 Summarits and 50/2 collapsible and early rigid Summicrons)] were inded "soft". These lenses are frequently found with hairline marks on the outer surfaces of the front and rear elements. Some time in the mid to late 1960s, Leitz switched to "hard" coatings, so very late 50/2 rigid and DR Summicrons less often have these hairline coating marks (although they frequently contain the ubiquitous internal fog).

All of the recent Leica lenses have hard coatings and are more resistant to scratches, though I wouldn't put a cigarette out on one. FWIW, I always use UVa filters on expensive Leica lenses. As one expert put it, 'it's better to keep your lenses clean than to keep cleaning your lenses'.

-- Eliot (erosen@lij.edu), April 25, 2002.

Perhaps you're spending too much time "cleaning" your lenses. Unless you accidently get a fingerprint on there, there's usually no reason for anything more than blowing off a bit of dust. One trick for that is to blow across the lens (actually from a bit behind it), because that way you're not spitting on it and also the turbulence tends to pick up the dust particles. When I get to the point of feeling the need to clean a lens, I figure that one attempt should be enough. I get a piece of lens tissue pretty wet with lens cleaning fluid and make a couple of good swipes across the lens. Then perhaps two more with a new tissue, and that's it. There might be a very small amount of smearing at one place or another on the lens that you can see if you move it around to just the right angle, but that's better than a bunch of "swirl marks" or gouges from excessive cleaning. I have several Leica lenses used continuously by my grandfather and myself since the early 1950s that don't have any cleaning marks on them...

-- Doug Hagerman (dhagerman1@aol.com), April 26, 2002.

Unless you have a fingerprint or something wet such as saliva from constantly blowing dust off of your lens I find the best way to remove dry substances, such as dust, is to use a soft brush. Get a good quality SOFT camel hair brush the kind used for water color painting from an art store. A #4 or #5 will do and costs around $15. First shake off any dust that might be in the brush then rub briskly against a clean cloth surface, like a shirt or pants leg to make the brush tip positively charged. (the same theory when you rub a balloon the same way and attach it to a wall) Next gently wipe the brush against the lens in a circular motion. Because the brush is "charged" it will easily pick up all of the dust particles.If you do this a few times every particle will be removed and the lens will sparkle.This method is also useful in removing dust from the surrounding area along side the lens and in collecting dust from the inside of the lens cap. (Why put a dusty cap on a clean lens) I have been doing this for years and it works.

-- Gerry Widen (gwiden@alliancepartners.org), April 26, 2002.