Vickko
Veteran
Has anyone here fixed their own cleaning marks on a lens?
For example, is anyone here also an amateur telescope maker?
Is polishing out the cleaning marks hard? I wouldn't think so, with the proper setup.
Then, what about putting on an anti-reflective coating? I can't conceive of doing that at home, but, what about a UV-cure spin-coated film?
regards,
Vick
For example, is anyone here also an amateur telescope maker?
Is polishing out the cleaning marks hard? I wouldn't think so, with the proper setup.
Then, what about putting on an anti-reflective coating? I can't conceive of doing that at home, but, what about a UV-cure spin-coated film?
regards,
Vick
mjflory
Accumulator
Hi Vick,
I've fixed -- or tried to fix -- more than just cleaning marks. I picked up a severely damaged thin Tele-Elmarit (Leitz 90/2.8) for a few dollars at a thrift shop. The rear elements were surprisingly good, but the front element had a strange sort of decay on it, as if a solvent had worked its way into the glass, or at least into the coating. The lens was unusable as it was.
Not knowing what it was, I tried removing the substance at first with water, then with alcohol, then acetone, all to no avail. As I had nothing to lose, I finally set out to repolish the element. I'd never done that before, so my first efforts, with the polishing compound I'd gotten with a Dremel tool kit, probably caused some damage. I looked into telescope-makers' methods a little, though, and eventually got a set of grits and polish on the 'Bay. I don't have the seller's name handy, unfortunately, but if you search for cerium oxide I think you'll find some sources. Cerium oxide is a fine-grained polish -- much finer than grit -- that is used on optical surfaces.
I polished by hand until I felt I'd never finish, then gave in and used the Dremel tool with a buffer as gently as I could. Eventually I reduced the damage to a level at which the lens was usable, but there does seem to be some irregularity in an image reflected from the surface of the front element, indicating that I've changed the refraction slightly. The lens does take much more acceptable photographs than it did, but I'm not so sure it's all that a Tele-Elmarit could be. (I'm sorry I don't have any test shot scans handy, but the test shots taken wide open were still rather hazy, while the lens seemed reasonably sharp and contrasty by F5.6 or F8.)
Eventually I bought another of the same model lens here on RFF, one with the more common haziness in the rear elements and a much better front element. When I have a little free repair time I'm going to make one lens out of the two with the best elements -- and test it against a lens comprised of the worst elements just to see how much difference I can see.
Before buying another lens I looked into just getting the front element repolished professionally. John at Focal Point felt it wouldn't be worth the cost that would be involved, as the setup for one lens element is as elaborate as for a batch. But he was able to tell me what, in all likelihood, had caused the damage. Apparently a rubber lens hood left in contact with the lens surface for a long time can decay and damage the coating in just such a manner!
I've strayed from your question quite a bit, though. All in all, I wouldn't advise undertaking a repolishing if the lens is usable as is, and even if it isn't I'm not sure it's worth the effort. I've never made a telescope lens, so I don't know just how one manages to give the surface a proper and uniform curvature. Clearly I failed at that with my amateurish methods, but perhaps someone with more patience and skill might manage it. As for coatings, they are applied in a vacuum chamber, and multicoating requires several coatings of different thicknesses to cancel reflections of different frequency ranges. I can't imagine how that could be done without an expensive setup and quite a bit of experience, not to mention the proper compounds.
Unfortunately, it seems that professional repair of an element is quite expensive. I've thought about seeing if I could measure the focal length of damaged elements precisely and buy a multi-coated replacement element from someplace such as Anchor Optics or Edmund Scientific. But even their large selections of sizes and focal lengths are probably unlikely to include the exact element one is seeking.
Good luck in any case. I wonder if others have other suggestions... Are there compounds with a refractive index similar to optical glass that will fill scratches?
I've fixed -- or tried to fix -- more than just cleaning marks. I picked up a severely damaged thin Tele-Elmarit (Leitz 90/2.8) for a few dollars at a thrift shop. The rear elements were surprisingly good, but the front element had a strange sort of decay on it, as if a solvent had worked its way into the glass, or at least into the coating. The lens was unusable as it was.
Not knowing what it was, I tried removing the substance at first with water, then with alcohol, then acetone, all to no avail. As I had nothing to lose, I finally set out to repolish the element. I'd never done that before, so my first efforts, with the polishing compound I'd gotten with a Dremel tool kit, probably caused some damage. I looked into telescope-makers' methods a little, though, and eventually got a set of grits and polish on the 'Bay. I don't have the seller's name handy, unfortunately, but if you search for cerium oxide I think you'll find some sources. Cerium oxide is a fine-grained polish -- much finer than grit -- that is used on optical surfaces.
I polished by hand until I felt I'd never finish, then gave in and used the Dremel tool with a buffer as gently as I could. Eventually I reduced the damage to a level at which the lens was usable, but there does seem to be some irregularity in an image reflected from the surface of the front element, indicating that I've changed the refraction slightly. The lens does take much more acceptable photographs than it did, but I'm not so sure it's all that a Tele-Elmarit could be. (I'm sorry I don't have any test shot scans handy, but the test shots taken wide open were still rather hazy, while the lens seemed reasonably sharp and contrasty by F5.6 or F8.)
Eventually I bought another of the same model lens here on RFF, one with the more common haziness in the rear elements and a much better front element. When I have a little free repair time I'm going to make one lens out of the two with the best elements -- and test it against a lens comprised of the worst elements just to see how much difference I can see.
Before buying another lens I looked into just getting the front element repolished professionally. John at Focal Point felt it wouldn't be worth the cost that would be involved, as the setup for one lens element is as elaborate as for a batch. But he was able to tell me what, in all likelihood, had caused the damage. Apparently a rubber lens hood left in contact with the lens surface for a long time can decay and damage the coating in just such a manner!
I've strayed from your question quite a bit, though. All in all, I wouldn't advise undertaking a repolishing if the lens is usable as is, and even if it isn't I'm not sure it's worth the effort. I've never made a telescope lens, so I don't know just how one manages to give the surface a proper and uniform curvature. Clearly I failed at that with my amateurish methods, but perhaps someone with more patience and skill might manage it. As for coatings, they are applied in a vacuum chamber, and multicoating requires several coatings of different thicknesses to cancel reflections of different frequency ranges. I can't imagine how that could be done without an expensive setup and quite a bit of experience, not to mention the proper compounds.
Unfortunately, it seems that professional repair of an element is quite expensive. I've thought about seeing if I could measure the focal length of damaged elements precisely and buy a multi-coated replacement element from someplace such as Anchor Optics or Edmund Scientific. But even their large selections of sizes and focal lengths are probably unlikely to include the exact element one is seeking.
Good luck in any case. I wonder if others have other suggestions... Are there compounds with a refractive index similar to optical glass that will fill scratches?
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nodyad
Member
Vick,
In my opinion, it is not worth trying to fix cleaning marks on a lens. If the depth of the mark is only in the coating itself (and most are), then the optical effect on the image is probably minor--anything you do to make it "look better" will probably do worse things for the imaging capability of the lens.
If there are actually small nicks or gouges in the surface, the sides of such gouges might introduce a bit of flare into the image. Even in this case, the flare does not affect sharpness so much as the contrast in some bright scenes. By filling such nicks with black paint (just rub in a TINY bit with your finger, wiping the rest away with a clean cloth before it dries), the cause of the flare is basically filtered out, leaving the resulting image nearly as-new. That is the most that I would advise doing to a user-grade lens with obvious scratches or gouges into the surface.
Michael,
Most opticians would not recommend hand polishing a lens because this leaves local variations in the curvature of the surface. The deformation your lens had was probably beyond repair, so whatever use you are able to get after your efforts is goodness, but don't pass that lens on as good--it is still compromised in terms of its original capability.
Professional regrinding and recoating is costly because these shops use mechanized polishing tools, and professional opticians will continuously check the overall accuracy of the new curve to the original optical standard of the lens--sometimes deviations as little as a few millionths of an inch matter a great deal! And they will check the resulting image across the field for even quality. Such treatment is a last resort for lenses that are very rare or worth the expense of restoring.
If the surface condition truly concerns you, buying a better lens always a non-invasive way to fix the problem! Mixing elements from two lenses will probably work okay, but if you later resell such a reconfigured lens, be sure to let the buyer know.
In my opinion, it is not worth trying to fix cleaning marks on a lens. If the depth of the mark is only in the coating itself (and most are), then the optical effect on the image is probably minor--anything you do to make it "look better" will probably do worse things for the imaging capability of the lens.
If there are actually small nicks or gouges in the surface, the sides of such gouges might introduce a bit of flare into the image. Even in this case, the flare does not affect sharpness so much as the contrast in some bright scenes. By filling such nicks with black paint (just rub in a TINY bit with your finger, wiping the rest away with a clean cloth before it dries), the cause of the flare is basically filtered out, leaving the resulting image nearly as-new. That is the most that I would advise doing to a user-grade lens with obvious scratches or gouges into the surface.
Michael,
Most opticians would not recommend hand polishing a lens because this leaves local variations in the curvature of the surface. The deformation your lens had was probably beyond repair, so whatever use you are able to get after your efforts is goodness, but don't pass that lens on as good--it is still compromised in terms of its original capability.
Professional regrinding and recoating is costly because these shops use mechanized polishing tools, and professional opticians will continuously check the overall accuracy of the new curve to the original optical standard of the lens--sometimes deviations as little as a few millionths of an inch matter a great deal! And they will check the resulting image across the field for even quality. Such treatment is a last resort for lenses that are very rare or worth the expense of restoring.
If the surface condition truly concerns you, buying a better lens always a non-invasive way to fix the problem! Mixing elements from two lenses will probably work okay, but if you later resell such a reconfigured lens, be sure to let the buyer know.
mjflory
Accumulator
nodyad said:
Don, thanks for the caution. No, I wouldn't dream of passing the lens on without a full description... I can't really imagine that the "bad front / bad back" lens would be of much use to anyone anyway.
I'm curious to see how the "hybrid" lens will perform, but I know too that I don't have anything approaching the skill, equipment, or perhaps even patience to perform a professional alignment and collimation. But I do enjoy doing what repairs I can with equipment that's uneconomical to repair.
payasam
a.k.a. Mukul Dube
Enjoy the rainbow, but don't be disappointed if there's no pot at the end of it.
DrLeoB
Shoot a IIIc "K" !!!
Actually, it is relatively straight-forward to make a new lens using amateur telescope techniques. You just have to do some reading and practice...practice... practice..
Anyway, 1/10 wave optics are regularly created in garages all over the world using these techniques. What you need is all of the optical measurements to good accuracy.
A/R coating is also possible in a garage, all you need is a diffusion pumped vacuum system with some electrical feedthroughs and a 10 amp battery charger to provide the current for a filament in the system. Magnesium Fluoride is the material commonly used for the purple-ish A/R coatings on most consumer lenses today. You put the MagFluoride in a little basket shaped filament a few inches away from your optics, pump the system down to 10-6 torr,heat the filament to white heat until all the MagFluoride is gone and shut her down, allowing the optics to cool before releasing the vacuum.
Good, restorable optical coating vacuum systems are routinely available on e-bay for less than $500. Power requirements are about the same as a swimming pool filter motor.
I worked for a custom optics manufacturer for a while and we always used surplus equipment to do this kind of low tolerence coating. We also did multi-layer coatings which were considerably more complex (up to 7 layers) and used much more esoteric chemals (Hafnium fluoride, Yttrium oxide...). These coatings are more for the UV or IR optics and are not really something the home amateur should tackle without significant experience.
Anyway, 1/10 wave optics are regularly created in garages all over the world using these techniques. What you need is all of the optical measurements to good accuracy.
A/R coating is also possible in a garage, all you need is a diffusion pumped vacuum system with some electrical feedthroughs and a 10 amp battery charger to provide the current for a filament in the system. Magnesium Fluoride is the material commonly used for the purple-ish A/R coatings on most consumer lenses today. You put the MagFluoride in a little basket shaped filament a few inches away from your optics, pump the system down to 10-6 torr,heat the filament to white heat until all the MagFluoride is gone and shut her down, allowing the optics to cool before releasing the vacuum.
Good, restorable optical coating vacuum systems are routinely available on e-bay for less than $500. Power requirements are about the same as a swimming pool filter motor.
I worked for a custom optics manufacturer for a while and we always used surplus equipment to do this kind of low tolerence coating. We also did multi-layer coatings which were considerably more complex (up to 7 layers) and used much more esoteric chemals (Hafnium fluoride, Yttrium oxide...). These coatings are more for the UV or IR optics and are not really something the home amateur should tackle without significant experience.
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mjflory
Accumulator
DrLeoB said:
Someday I would love to try it. It's fascinating to imagine that one could do coatings in one's garage, too! (Alas, I don't have a garage, much less a vacuum oven, but it sounds like fun.)
I miss California! (Garages, swimming pools...)
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Spyderman
Well-known
Nice reading, but back to the original question:
if the marks are only in coating it won't have much effect on your pictures. Even if there are just a few big scratches in glass - it won't affect the pictures sharpness, it micht however cause flare ald lower overall contrast. You can do more harm than good by trying to repair cleaning marks.
If the lens has uniformly scratched almost the entire area, it might be usable, but I wouldn't recommend trying to polish it. You'd change the properties of the lens.
If I remember correctly Brian Sweeney some time ago wrote about some "glass repair kit". It is a liquid, which you apply on the lens to fill the scratches...
if the marks are only in coating it won't have much effect on your pictures. Even if there are just a few big scratches in glass - it won't affect the pictures sharpness, it micht however cause flare ald lower overall contrast. You can do more harm than good by trying to repair cleaning marks.
If the lens has uniformly scratched almost the entire area, it might be usable, but I wouldn't recommend trying to polish it. You'd change the properties of the lens.
If I remember correctly Brian Sweeney some time ago wrote about some "glass repair kit". It is a liquid, which you apply on the lens to fill the scratches...
Freakscene
Obscure member
Robin Harrison
aka Harrison Cronbi
nodyad said:
Very interesting. I have a CV Ultron 28mm with a tiny nick about two thirds of the way from the centre of the front element to the rim. I can't help but wonder how much of an effect it is having, and generally don't shoot with it in bright light.
The paint idea is a new one on me, but I would be extremely concerned rubbing paint onto a front element! I suppose the problem with a nick is the depth of the problem prevents any polishing option.
Any alternative suggestsions? As this is a current production lens, I take it I could source a replacement front element, but at a high cost?
Robin.
I have. I bought a collapsible Summicron on Ebay to use for parts to fix another lens with a bad inner element. So I had a great lens and an unusable lens after doing the parts-switch.
With nothing to lose, I experimented on the Bad lens.
I used polishing film from 3M, because I has some around. Cerium Oxide would be better. I used an Eyeglass coating repair kit to recoat it. It is a "paint on Lacquer". It works, but you need to practice with it. I learned not to revisit areas, just put on a coating starting from the center and work outward. Let the force of gravity flow the fluid. Cover the glass to keep dust off, and let sit for a day. Don't like it, use Isopropyl alchohol to remove it. Keep a filter on the lens after this treatment.
Unless the lens is severely damaged to the point of being unusable, and the lens is not worth having done professionally, I would not do this.
Before:
After:
With nothing to lose, I experimented on the Bad lens.
I used polishing film from 3M, because I has some around. Cerium Oxide would be better. I used an Eyeglass coating repair kit to recoat it. It is a "paint on Lacquer". It works, but you need to practice with it. I learned not to revisit areas, just put on a coating starting from the center and work outward. Let the force of gravity flow the fluid. Cover the glass to keep dust off, and let sit for a day. Don't like it, use Isopropyl alchohol to remove it. Keep a filter on the lens after this treatment.
Unless the lens is severely damaged to the point of being unusable, and the lens is not worth having done professionally, I would not do this.
Before:
After:
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Taken with this lens;
At F4:
Wide-Open:
Back to F4, distance shot:
At F4:
Wide-Open:
Back to F4, distance shot:
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oldrangefinderguy
Member
Nice job, Brian.
I have an old collapsible Sonnar for Contax mount with a front surface that looks remarkably like your before picture. It has a rear surface that looks the same. I guess there's little to lose by experimenting. Can you describe in more detail your method for removing the coating?
If I can't fix the old glass, I've also wondered whether it would be possible to swap out the Zeiss elements for the elements out of a Jupiter 8. The J8 is supposed to be an exact copy, but how exact is exact in this case?
Anyway, I'd try your method first. Seems to have worked fine for you.
Randy
I have an old collapsible Sonnar for Contax mount with a front surface that looks remarkably like your before picture. It has a rear surface that looks the same. I guess there's little to lose by experimenting. Can you describe in more detail your method for removing the coating?
If I can't fix the old glass, I've also wondered whether it would be possible to swap out the Zeiss elements for the elements out of a Jupiter 8. The J8 is supposed to be an exact copy, but how exact is exact in this case?
Anyway, I'd try your method first. Seems to have worked fine for you.
Randy
R
Rodinal Addict
Guest
What about fungus, inside the lens? I have a Rokkor 58mm, f1.4, with a dot , maybe 2mm, right in the dead center of the front element. If I can get this front element off, are there ways to polish this fungus off?
Robin
Robin
Kim Coxon
Moderator
It will depend on how severe the fungus is and more importantly which strain of fungus it is. In most cases, it does clean quite well. Do not try to "dry" polish it but use a lens cleaning fluid such as Calotherm. With certain strains, they release an acid in the more advanced phases and this acid etches the glass. If this has happened the lens is a goner. The acid attacks not just the coating but the glass itself.
Kim
Kim
Rodinal Addict said:
I took the element out of the lens and polished using circular motions. Just put on the TV, sat it down, and gave it a whirl. Checked every few minutes. This is tedious work. If I ever try this again, it will be with cerium oxide powder and a polishing cloth. Kits are available on Ebay and other places- basically used for making telescope mirrors in the garage or basement. I had a friend in high-school that ground an 8" telescope mirror. Figured if he could do that at age 16, I could give this a try.
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Vickko
Veteran
Ah, that's the spirit. I figure that there must be methods to deal with this "at home".
I ran across the eyeglass methods and ads. Sounds a bit like snake oil. I can only assume that this method (grind off coating, recoat with magic eyeglass compound), won't ever get back to the original MTF performance.
My lens is a Nikkor 50mm f1.1 - pretty rare. And the condition isn't anywhere as bad as you have on your lenses. I took photos with the lens on the weekend - the photos look fine. Good and sharp and contrasty.
And on my lens, I can't (haven't even tried) to remove the front element. The lockring is a very steep taper, and no lockring notches. It would need the special magic tool to remove it, and I don't have one. I'm not going to risk marring the front ring, trying to take it off.
Anyway, thank you for your stories of daring.
That's what I love about this group!
And if you ever need your 50mm f1.1 repaired, call me.
Vick
I ran across the eyeglass methods and ads. Sounds a bit like snake oil. I can only assume that this method (grind off coating, recoat with magic eyeglass compound), won't ever get back to the original MTF performance.
My lens is a Nikkor 50mm f1.1 - pretty rare. And the condition isn't anywhere as bad as you have on your lenses. I took photos with the lens on the weekend - the photos look fine. Good and sharp and contrasty.
And on my lens, I can't (haven't even tried) to remove the front element. The lockring is a very steep taper, and no lockring notches. It would need the special magic tool to remove it, and I don't have one. I'm not going to risk marring the front ring, trying to take it off.
Anyway, thank you for your stories of daring.
That's what I love about this group!
And if you ever need your 50mm f1.1 repaired, call me.
Vick
mjflory
Accumulator
Good and sharp and contrasty -- It sounds good to me! Might be just as well to leave well enough alone. But you've started a very interesting thread (and a good start for the optics and lenses forum).
I don't know Nikon lenses, but this sounds like an impressive one.
I don't know Nikon lenses, but this sounds like an impressive one.