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on Jun 19, 2016 20:04:00 GMT
Posted: Jun 19, 2016 20:04:00 GMT
This lens can be saved? ML 21mm   |
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on Jun 21, 2016 1:04:27 GMT
Posted: Jun 21, 2016 1:04:27 GMT
That. Is. Nasty.
If it's just fungus, that can be treated, and mostly removed, though it may leave an etching behind. If it's mostly scratches, what you now have there is a soft portrait lens, just as long as your subjects don't mind the distortions.
You could swap it with another element, but the lens would likely never be the same. It could be sent in for an expensive grinding and coating fix, but there aren't many places left that offer that service.
I think it's a goner.
PF
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on Jun 21, 2016 2:02:00 GMT
Posted: Jun 21, 2016 2:02:00 GMT
I'm afraid ridgeblue is probably correct - it's terminally damaged.
Although there's a small area that looks like fungus, looking at the fine lines and pattern, most of the damage seems to be in the form of scratches; it looks like someone tried to clean the front element with a pan-scourer. It could be partly saved as was said by re-grinding and coating BUT not only will that cost more than a mint condition second-hand lens, with that amount of scratching, the re-grinding will certainly change the geometry of that element such that it may never give the quality of image for which the lens is renowned.
I have heard that some people have been able to use silicon to fill in light scratches on a lens and then use it with some success. It is often possible to use a lens with such a scratched front element to good effect under neutral lighting conditions where the object being photographed has high contrast, but any strong light source will probably result in a diffuse, low contrast photo. I always remember a photograph of a Zeiss 50 1.4, made for Rollei, which had a cracked, not just scratched, front element and a large insect inside it; it was still able to produce excellent photos until it was pointed into direct sunlight.
It's a tragedy but it will be a lovely paper-weight. Of course, it is always worth keeping the lens because, at some stage, one may well appear that has damage to the rear elements or aperture assembly and you can use it is a donor to replace your front element. You just never know.... |
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on Jun 21, 2016 8:37:52 GMT
Last Edit: Jun 21, 2016 8:38:10 GMT by dragos
Thank you for your answers.
I am wondering if the front element is the same from another lens. At first view for ex seems the 200mm has similar lens.
I was not able to dismount mine. Has anyone an ml 200mm disassembled or can take a look at the first element?
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on Jun 21, 2016 21:37:37 GMT
Posted: Jun 21, 2016 21:37:37 GMT
I have a faulty 70-210 4.5 which I can send you, but with strong doubts. I'd never thought that lenses could share their elements.
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on Jun 22, 2016 1:48:15 GMT
Last Edit: Jun 22, 2016 1:48:48 GMT by ridgeblue99
I seriously doubt an element from a lens other than the same model as your 21mm would work. Likely the geometry would be different, even if the size was the same.
As for getting another lens with with the opposite damage, I was looking into that myself on a 24mm Nikkor. After adding up the two with shipping costs, I could still get a mint looking example with caps and hood for less money.
PF
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on Jun 22, 2016 18:54:40 GMT
Posted: Jun 22, 2016 18:54:40 GMT
You could only substitutre this element with an equal one taken from another 21mm to be scrapped. Lens design implies extremely precise tolerances in lens shape and type of glass. Performance of a lens not only depends from the shape of the two curvatures, but also from the glass refraction index. So matching lenses to correct aberrations results in unique designs. High order system of equations must be resolved by inventive engineers to create a lens. I think you will have a paperweight, unless somebody will give you a donor lens with the front element intact. In that case you might safely use it. 60 |
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on Jun 24, 2016 12:57:33 GMT
Posted: Jun 24, 2016 12:57:33 GMT
I was today to a optician. They measured the lens and apparently thy can produce a new one, identical, with same characteristics,identical. There is a big range of glass brands, including zeiss. A good quality mineral glass, with anti reflex coating included will cost me around 140 Euros.
To try or not?
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on Jun 24, 2016 18:49:22 GMT
Posted: Jun 24, 2016 18:49:22 GMT
Hi dragos,
If they will give you a written guarantee that the lens will be identical then I would go ahead as that is a lot less than the cost of a second-hand ML 21mm lens in top condition.
Good luck!
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on Jun 25, 2016 15:12:54 GMT
Posted: Jun 25, 2016 15:12:54 GMT
I was today to a optician. They measured the lens and apparently thy can produce a new one, identical, with same characteristics,identical. There is a big range of glass brands, including zeiss. A good quality mineral glass, with anti reflex coating included will cost me around 140 Euros. To try or not? g The lens might be identical from the point of view of curvature, but the refractive index and Abbe number of the glass might differ greatly from original. From what I gathered this parameter is as important as the curvature in the calculations for creating the lens. This scientific paper gives an idea of the complexity of the task It might even work better, it might probably not. Maybe it could give decent results but I wouldn't waste such big money see this en.wikipedia.org/wiki/Abbe_numberthis paper gives an idea of the complexity of the parameters involved www.optics1.com/pdfs/removing_mystique.pdfAnd they are just talking simple doublets here ... 280 |
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on May 13, 2017 22:12:22 GMT
Posted: May 13, 2017 22:12:22 GMT
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