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View Full Version : Lens repolishing - Who does a good job?



JBAphoto
11-Aug-2012, 18:41
Hello,

I have a 135mm Symmar that came to me years ago with a mass of tiny fine cleaning marks - I now have a nice newer old one, but would prefer to have the scratched on repolished rather than bin it - 135mm is my "standard" 5x4" landscape length

Who is a good lens re-polishing company?

Please PM me if you have any recommendations, as I can never find old posts of mine in the plethora of information on this site

John
mail2@jbaphoto.com.au

Steven Tribe
12-Aug-2012, 10:58
The answer I always give is that lens surfaces cannot be even lightly polished unless you have the original tools used in manufacture, or make a new tool using the exact known surface radius!
Anyone (or company) who says they can polish out scratches without changing optical characteristics is either ill-informed or deliberating misleading customers.

John Jarosz
12-Aug-2012, 12:28
+1

John

Leigh
12-Aug-2012, 13:38
If the marks are deep enough to be visible, you cannot repolish it without changing the optical characteristics of the lens.

By definition you're changing the thickness of the element, even if you manage to maintain the proper radius and optical axis, which is unlikely.

- Leigh

Drew Bedo
12-Aug-2012, 14:10
I am sure that Steven, John and Leigh are right about this.

With that said:


Is Schneider an option?

Given that Schneider is not an option and "The Bin" is the next stop for this lens: What about an eye glass maker or optician shop?

In any case, hold on to the whole lens/shutter. You may be able to find a donor for the front elements someday. Stranger things have happened.


Again; I recognize that the three named posters are correct in their recomendation against republishing.

Sevo
12-Aug-2012, 14:41
Feasibility aside (it can only be done without hurt to the lens performance if the damage is strictly limited to the coating), it would be rather a waste of money on a cheap lens like a 135mm Symmar - whose going rate is quite a bit below what I'd expect or disassembly, etching and re-coating a front lens.

Vaughn
12-Aug-2012, 15:03
How about doing a comparison between the old and the new lenses to see if there is any actual difference in image quality?

Kevin Crisp
12-Aug-2012, 16:01
Focal Point in Colorado can handle it. They will tell you if the scratches are deep enough to snag a fingernail, they will not polish out. After you polish, you have to recoat. If the front lens surface is glued to the one behind it (something I don't know since I've never reglued a Symmar) they must be separated for recoating, then reglued. Focal Point does a great job. Is it cost effective on a lens worth $250 or so? No.

Lewand2owski
12-Aug-2012, 17:03
In any case, hold on to the whole lens/shutter. You may be able to find a donor for the front elements someday. Stranger things have happened.
http://www.aofp.info/sun1.jpg
http://www.aofp.info/sun2.jpg
http://www.aofp.info/sun3.jpg
http://www.aofp.info/sun4.jpg

Jim Andrada
12-Aug-2012, 17:57
And I wouldn't consider an eyeglass maker seriously either. I once had a project to automate the lens grinding labs at American Optical and did a feasibility study with B&L

Pretty cut and dried and basic stuff before they got into casting the current plastic lenses that we all use today. Definitely not of the level of optical perfection needed for a camera lens. Funny - they wanted my company to provide an optical engineer as part of the deal because all of their engineers were working on satellite surveillance systems that could count the fleas on a Chihuahua from earth orbit and had no interest im something as mundane as eyeglasses.

Kirk Gittings
12-Aug-2012, 18:48
I had Focal Point repolish a lens for me many years ago after it fell face first into some gravel. It worked very well afterward, but the coating was not as durable as the original MC.

Tim Povlick
12-Aug-2012, 19:22
Hi John,

PM sent

I've used:
http://www.focalpointlens.com/fp_intro.html

for two lenses that had condition about like you describe. One, a Kodak Commercial Ektar 14" that is now like new. FP did an excellent job. They also state the new coating is tougher than old coatings because it's put on at a higher temperature. One of the lenses I sent back had a ton of micro-scratching that when looking through it appeared to have a softer focus and reduced contrast. After repair this effect was gone and the lens looked much clearer. Wish I had done before / after on that one. Cost is pretty steep, but matches level of expertise.

Concerning deeper scratches I've glanced at a lot of Telescope ATM books / articles and it seems one can measure the radius without to much trouble. A hard pitch tool could be made to do the heavy grinding and then a softer pitch tool for polish / lap. Never done this and since it's not germane to the problem at hand, not worth worrying about.

Good Luck and Best Regards,

Tim

Jim Michael
12-Aug-2012, 19:24
There's more to it than getting the thickness and curvature correct. The lens elements together make up a system that is optimized for one or more wavelengths and the refractive index of each element is part of the formula. Your lens maker would need a blank of the appropriate refractive index and grind it to match the formula. Otherwise you may end up with chromatic and other aberrations.

Bill Burk
12-Aug-2012, 21:13
I had a Dallmeyer telephoto polished by Pacific Universal in Pasadena, they explained before they took the job that they were going to leave the deep scratch. But they removed many fine hairline scratches and recoated the lens. So if you are considering the repolishing to solve deep scratches, I agree with the consensus that it would be difficult. If there are fine scratches, those may be fixable.