 Posted: Tue Jan 10, 2012 10:44 am Post subject: |
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Sevo wrote:
| aoleg wrote: |
We can. Compare several versions of Jupiter-9 that have different coatings, and it's very easy to see the difference in colors (or do you really believe that the factory used green or brown "bottle glass" to make these lenses?)
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Glass tints used to be quite an issue, even tiny contaminations can stain glass visibly and clean-room condition platinum pot melting in electrical ovens only evolved slowly. The most dramatic improvements to glass clarity only occurred in recent times when intercontinental fibre lines opened a new market where it made a significant difference whether glass still was transparent after 50m or 50km.
Many of my old uncoated lenses have visibly brown or green elements. And I suspect most of the later ones with tinted elements to have glass issues too. It should be possible to spot a coating-induced tint, as the coating reflection and complimentary transmissive tint change in colour and show little change in intensity when viewed at an oblique angle, while a glass stain will keep colour and increase in intensity.
| aoleg wrote: |
It's been done from the 60's with single-coated lenses, I believe. Look at some old 100mm f/2.8 lens; they'll have amber coated front group and blue/purple coated rear group. |
Might be, yes. But it is hard to tell whether these were tuned with a custom anti-reflex coating, had a dedicated filter coating or even were their first field trial multicoatings - that amber front was even more characteristic of the first few years of Nikon MC lenses.
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Sevo |
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