Impact of cleaning marks

[m.bruehl]

Hi,

I did some searching, but found no really illuminating answer:

I just got an 8/165 SA, and was happy as can be - until I held it against the light. The surface of the front lens - that looked absolutely O.K. on first view - was sort of matte, sometimes a little blue or green colored. Upon closer inspection I saw, that the complete front lens showed microscratches in coincidal distribution. Depending on the viewing angle the surface seemed absolute normal or looked like a frozen sea after days of ice-skating.

You may call me picky, but I am afraid that this amount of "cleaning marks" has an impact on contrast and sharpness, even if I take photos using a shade/compendium to prevent direct light from the sides.

What do you think about it?

Regards

Michael

[walter23]

I have a schneider 150/265 with some light fog inside that is only visible under very specific lighting glancing the internal element just right. It seems to have lower contrast than my other lenses, but my others are also newer designs with better quality coatings so I'm not sure how much is a consequence of the fog. I'm pretty sure the fog is decreasing contrast a bit though. So far this has been more of a benefit than detriment to my photography with the lens :)

The only way you'll know is to test the lens for yourself. Put the lens through its paces, shoot in backlighting, etc, and see what happens.

[rob]

It could be scratches on the coating itself, not the glass. Some of my lenses and filters have a lot of "cleaning marks", but they perform just fine. May be my habit of using shade helps. I would say, try it first.

[Peter K]

Cleaning marks, also "only" in the coating, can ruin the performance of a lens. With a WA lens like the SA and it's 100° angle of view a shade won't help much. So as said before, test the lens and when contrast and sharpness suffers, ask at Schneider if the lens can be repaired.

[m.bruehl]

Thanks for your comments.

What setting would you propose to test on decrease of contrast/sharpness, if you don't have the same lens with perfect surface available?

I have a test-sheet, so I could take some 6x9 with my 90 mm, which also has a very curved front lens, but this is a new lens with coating. So if I see a difference, I don't know if it's due to the lens or the cleaning marks ...

Or do you think about taking an outdoor picture and just say "Hey, seems to be O.K. for me"?

Any help appreciated.

Michael

[Brian Vuillemenot]

I highly doubt that the cleaning marks will have any noticable effect on the performance of the lens. I have lenses that have sustained considerably worse damage than you describe (including taking a small chip out of the front element) with no visable difference in performance after the damage.

[Glenn Thoreson]

The short answer: Only you can tell if it will be acceptable. If some test shots look okay to you, it's good to go. If you can't make it perform, get rid of it.

[Dan Fromm]

Michael, cleaning marks' effects on the final image depend on the marks and on the lens. Just ask y'r 165/8 SA whether it shoots well enough for you. If it does, use it and be happy. If it doesn't, don't use it and be unhappy.

I give you this advice because I have three lenses whose front elements have the classic "cleaned with a scouring pad" look. Two of them -- 210/5.6 Saphir, 210/6.3 Prinz (= Commercial Congo) -- are still very usable. The third, an 80/2.8 Xenotar, is just horrible.

Good luck, have fun,

Dan

[Peter K]

Michael, the front lens of the SA is nearly flat. But this isn't the problem. Some cleaning marks are normaly no problem also. In any case, the Super-Angulon is a lens with good contrast. So it should be easy to check the performance of the lens with some outdoor pictures. Or you can use Toepler's Schlieren method: put an illuminated diaphragm near the rear focal point of the lens. A white LED will also do the job. In some meters distance the image of the diaphragm will be projected on a roud screen with the same dimensions of the image of the diaphragm or LED. Behind this screen the lens will be observed with a telescope. The clean parts of the lens are dark, but every scratch, buble and so on is bright.

[David A. Goldfarb]

I've had one lens where I thought the cleaning marks were bad enough to create a noticably diffuse image, and I returned it to the seller for a refund. As the others have suggested, the only way to know with any given lens is to test it. Try photographing a high contrast scene, like an indoor scene looking out a bright window, and look for flare.

Remember that the surface of the lens is far from the focal plane, so physical lens defects aren't going to be anywhere near in focus. They just tend to add to veiling flare, and often not significantly.

[Peter K]

Remember that the surface of the lens is far from the focal plane, so physical lens defects aren't going to be anywhere near in focus. They just tend to add to veiling flare, and often not significantly.
But the front lens is very close to the entrance pupil. So any distortion is more or less visible on the image.

[Robert A. Zeichner]

With a WA lens like the SA and it's 100° angle of view a shade won't help much.

Not necessarily. Even if a lens just covers the 4x5 or 8x10 format, nearly 30% of the light that an unshaded lens projects toward the film is non-image forming light and much more than that for more rectangular formats like 5x7, 4x10, 7x17 etc.! I have a 165 mm Angulon that just covers 8x10 and which I use regularly on my 4x5 and 5x7 and is flawless in terms of the condition of the coating or glass. I've made extensive comparisons between otherwise identical negatives made with and without a proper shade and am amazed at the difference.

Take a look: http://web.mac.com/razeichner/iWeb/RAZP%20large%20pix/Shade%20pg%201.html

[IanG]

Well I have a Vivitar 150mm VHE enlarger lens with cleaning marks, these are only visible when looking through the lens. (The Vivitar glass is made by Schneider and is identical to a Componon). The prints made with it are sharp there is a noticeable drop in contrast compared to a similar Componon, and they lack the sparkle of a unmarked lens.

The link Robert posts above is probably equally true as a comparison for my lens.

Ian

[Kevin Crisp]

The obvious bottom line is what the negative looks like, but I have a quick way to sort out lenses that are likely to be trouble. Open it up and from a distance of 15' or so look at a single bright light. (A tensor lamp works well for this.) Is the light bright, with clear boundaries looking through the lens? If so, or if there is minimal diffused light around the source, you're going to be OK. If the cleaning marks cause the light to smear across the face of the lens or if the bright light has a good sized smear of light around it, this is likely to be trouble. A lens shade will help, but if the lens can't handle a highlight like that you are going to see it in a negative unless you stick with only moderately contrasty subject. Try it out to be sure.

[m.bruehl]

Dear all,

thank you again.

I am in laser business, so I did some testing with a laser line. Normally, if projected on glass, you can't see much of it, because it goes through. In certain types of glass or at certain angles you can guess where the line is, but seldom on the surface, it seems to be in the glass.

So I took my 17mm SLR lens and projected a line on the front glass - and made a picture of it (left, see below): TOK_17mm_600x600.jpg

Then I did the same with the SA 8/165. (right, see below): SA_165mm_600x600.jpg

For me, the difference is obvious, and I have problems imagining these (micro)-scratches have no or only little impact. And they are not only at a single place, but all over the lens.

Additionally, if I move a spot laser or a laser line over the surface, I often get a direct reflection of red light. The same should happen to all wavelenths.

So with this new information - specially the members who said it has little or no impact - still sure about that?

And yes, I will take some real pictures, too. But it will take some time.

Regards

Michael

[Peter K]

Robert, of course a well aligned shade or compendium will always help to avoid flare. But in this case with such a scrached frontlens also a lenshade will doesn't help.

[Dan Fromm]

Interesting, Michael.

You inspired me to ask a slightly different question with the help of my little laser pointer. That is, what happens to a ray that passes through the lens?

My horrible Xenotar produces a spot, as expected, with a wide brilliant halo. My horrible Zircon produces a spot too, but a tight and dim halo. Lenses believed to be clean and with good coatings produce a spot; with some there's no halo, with others there's a dim and very tight one. The same goes for most of the uncoated lenses I tried.

The big surprises are my two dialyte type Kodak Anastigmats. 170/6.3 and 203/7.7, both uncoated. But produce an ok central spot with a number of fairly bright spots off-axis. I've never shot the 170, but the 203 shoots fairly well.

Good luck, have fun,

Dan

[Mark Sawyer]

I have an old 12" Dagor that's very badly scratched and pitted front and rear, but it gives crisp, sharp negatives.

Then again, my 18" Verito has just the slightest trace of a cleaning wisp, and it's amazing how much it softens the image, especially wide open.

Guess you never can tell...

[Turner Reich]

Can a $15 solution hold the secret to scratch-free lenses on your eyeglasses?
Commercials for scratch repair kits claim to remove the surface scratches on your sunglasses, prescription eyeglasses -- even scratched up crystals on your watch.

We paid just over $16 including sales tax and found a volunteer to put it to the test.

Local Realtor Michael Valiente was actually volunteered by his family because he not only wears glasses, he's seen the commercials for the scratch repair kits and was curious.

The one we bought is called "Lens Dr." The box says it "Instantly Removes Surface Scratches from Prescription Glasses, Sunglasses, Watch Crystals and Work Goggles!"

"I'm skeptical about it," Valiente said. "It's a scratch. Seems to me you'd have to polish the glass."

Right out of the gate, we have problems. One of the bottles in the sealed plastic bag has been leaking for who knows how long.

The instructions are not only wet, the pages are stuck together. We do our best to peel the pages apart and figure out the 2-step process.

"Step one cleans. It's a cleaning solution and step 2 is a treatment solution," he said.

By now, Michael's so skeptical he doesn't want his glasses to be the guinea pig. So I brought along a pair of my old glasses and they are really scratched.

You can even see some of the scratches through our camera.

First step, spray the cleaning solution on the lenses, spread it over the lens with your finger, and wipe clean with the soft cloth in the kit.

Step two, apply the treatment solution. It's kind of like painting with a Q-tip. This presumably fills in the scratches.

Once the lens is evenly covered, let it dry.

As for how my glasses ended up: The treatment seems to make the scratches a little less visible but there's a glossy film.

Our skeptic says it might be fine in a pinch.... for someone else.

"But not my glasses," Michael said. "My glasses are very important to me, so I would probably not do that on my glasses."

Michael says leave it to the eyeglass professionals. And guess what the professionals told me?

We contacted a local optometrist and a major specialty eyeglass retailer and both had the same response -- they don't do scratch repair. There's no such animal.

They say the products being marketed are temporary fillers at best, but the ultimate solution to scratched lenses is new lenses.

In case anyone gets the idea to using a scratch remover as advertised on TV.

[E. von Hoegh]

A few slight marks will have little effect. Many marks will have a noticeable effect, first reducing the contrast then the sharpness.

Polishing out the marks will change the lens for the worse.

Most of my old lenses have a mark or two - by this I mean some very light fine wisps that are difficult to see under any conditions. One lens has an ugly looking scratch that you can feel with a fingernail, right in the middle of the rear surface. I blacked it out with India ink, and can see no effect. It's my favorite lens for 8x10, in fact - I just (tenporarily) remounted it while I invent a way to replace the composition aperture blades in the original Ca. 190? Compound shutter.

I have a 16 1/2" Artar that has a haze of "cleaning marks" on the front and rear surfaces. I use it primarily as a paperweight; it s**ks in comparison to a pristine example of the same era. I do shoot portraits with it; it's plenty sharp but the flare is intolerable.

[Brian Ellis]

If you can return it I'd do that. While "testing" the lens is fine, not all situations in which you photograph are equal. So who knows, you might make a bunch of test shots, everything might look fine, then one day you make a great photograph and it's ruined because of these marks. Remote possibility? Maybe, maybe not. So I'd return it if that's possible. If not, good luck.

[cyrus]

After I saw this (http://www.certo6.com/gallery/planar.html), I stopped giving too much of a damn about scratches, fungus, cleaning marks etc on the camera lens