what the heck are "cleaning marks" on a lens

[jlamarca]

always wondered - do some people use a brillo pad to clean their lenses?

and what's with the "clean and clear" so often used to describe used lenses? can't a lens be clean and clear (glass is clear, after all) and have a big old scratch on it at the same time? is a scratch (unerasable) worse than unclenliness (cleanable)? or does a small scratch rarely/never show up in a photo while fogging or fungus will degrade an image significantly?

 

[bmattock]

always wondered - do some people use a brillo pad to clean their lenses?

More lenses suffer from obsessive (and improper) cleaning than they do by having some slight amount of dirt on the, IMHO.

Any lens can be scratched by improper cleaning, even with delicate cleaning tools. It is the dirt itself that does the damage.

and what's with the "clean and clear" so often used to describe used lenses? can't a lens be clean and clear (glass is clear, after all) and have a big old scratch on it at the same time?

Sure it can. Often does. And everyone's understanding of a 'clean' lens differs. I've met some real lens peepers in my time - lenses they rejected as being trash, and I could not see the damage they could even with an 8x loupe and a lot of time. Other times, I've been the one to point out fungus, separation, and scratches that sellers someone could not see. It's all very subjective.

is a scratch (unerasable) worse than unclenliness (cleanable)? or does a small scratch rarely/never show up in a photo while fogging or fungus will degrade an image significantly?

Scratches can be removed - but generally not well, not worth it, and too expensive, unless your lens is an irreplaceable masterpiece - again, IMHO.

Scratches generally degrade image performance more than dirt - they scatter light, which lowers contrast and increases lens flare. The damage is usually such that only a direct comparison to the same lens in the same situation that does not have the damage will demonstrate the loss.

Scratches, however, can be - and have been since dot - filled with ink or black paint and ignored. Most people who know enough to do this will not do it, however, because most of us are obsessive-compulsive anal-rententives who won't be able to sleep at night with a scratched lens in our cupboard. I exclude myself from this group because I like a nice grungy lens on occasion, and being cheap, I've got my share of them.

The best thing most people can do with their lenses is keep the dust off 'em with a little air blown on them from time to time, protect them from the elements, and otherwise just pretty much leave them alone. But we won't, because we can't. And that's how we ruin our lenses.

Just my 2 cents.

 

[sepiareverb]

Some of the older lenses were more delicate than modern glass I believe. I've heard talk of 'soft' glass on some older Leica lenses.

 

[bmattock]

Some of the older lenses were more delicate than modern glass I believe. I've heard talk of 'soft' glass on some older Leica lenses.

I don't know how 'soft' the glass was, but prior to the introduction of lens coatings, glass was what you were cleaning, and it is fairly easy to scratch. After that (just prior to and after WWII), you were cleaning mostly lens coating. They also varied in 'hardness' and some coatings could be scratched - even rubbed through - without too much effort. Often the inner and (rear) elements of a lens were coated with less hardy coating material - the idea being that consumers would not routinely disassemble lenses to clean inside elements or that rear elements would not usually get dirty, being inside the camera and all.

Modern coatings are quite hard and comparatively hard to scratch. People can do it, though. We're determined little monkeys.

 

[sepiareverb]

Thanks for setting that straight. I've had a lens or two with what seemed like coatings rubbed through. Guess it was.

 

[peterm1]

One reason I like to use a UV filter is that there are times when you must clean a lens, and any amount of cleaning, no matter how careful is executed it is eventually going to have some effect on the surface of the lens/ filter. As I keep saying, sooner ruin a $30 filter than a $300 (or perhaps $3000) lens.

Marks and damage to coating do matter. I used to own a Nikon Nikonos U/W camera with its standard 35mm lens. When I bought it (new) it had a small circular flaw in the front surface coating. I never sent it back thinking it would not matter. But used above water that puppy flared like a maniac whenever I shot other than with the sun behind me. OK I think this lens had a reputation for flare anyway but the flare I got always corresponded with the position of the coating flaw and convinced me that the quality of coating and lens surfaces matters.

 

[jlamarca]

Interesting. Thanks for the responses. So for someone who prefers to not use a UV filter and leave the lens cap off, here's another question: what is worse, given that on most days, after walking all around nyc with wind and pollution etc, there are countless particles and a drop or three of who-knows-what on the surface of my lens, a) cleaning it at the end of every day (I'm using pec pads and alcohol) or b) leaving it alone with whatever is stuck on it and then cleaning it preiodically, like once a week? Of course a blower is probably best for the dust (I need to get one) but what about the droplets - there are always a couple and I've read that the sooner they are cleaned off the better.