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on Dec 28, 2020 10:30:07 GMT
Posted: Dec 28, 2020 10:30:07 GMT
Hi folks,
I've just been re-reading an old Yashica lens catalogue and spotted something which caused pause for thought.
We have accepted that the DSB lens range is single-coated unlike the ML series with its superior multi-coating; the prior DS-M range from the M42 era was also multi-coated.
In the catalogue just two DSB lenses are featured: the 55mm f2 and 50mm f1.9. However, the description of the latter has this sentence: Features a unique combination coating. There is no such reference concerning the 55mm lens.
I've always found the DSB 50 1.9 to be an excellent lens, sharper and with the same, good level of contrast of the ML f1.9 and it was the kit lens with the impressive, if heavy and old-school, FX-1. Might the 'combination coating' be a reference to multi-coating, perhaps as seen on Yashica's previous DS-M range? If so, it would go some way to explaining the excellent credentials of the DSB 50 1.9.
Just wandering...
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on Dec 28, 2020 14:09:55 GMT
Posted: Dec 28, 2020 14:09:55 GMT
I think the main "monkey wrench" in this discussion is that there is no actual definition of "multi-coating". And it was years after lenses received multiple coats that the term was ever created.
Minolta produced the first coated lens in Japan, in 1946. Later, Minolta pioneered what they called "Achromatic Coating" -- two layers of magnesium fluoride deposited in different thicknesses -- in 1958. So that's multiple coats. Is that multi-coating? By my definition it is. They continued to change/improve their "Achromatic Coating" over the years, but they never called it "multi-coating".
The same is basically true for all the lens makers -- although they came up with different names for their coating -- EBC, BBAR, T*, etc. Add to this that a "multi-coated" lens does not mean that all of the elements are multi-coated. Minolta literature states that their coatings are applied only where it is beneficial. It's entirely possible that only one element in a lens is multi-coated, and the manufacturer labels it "multi-coated".
My guess is that the two DSB lenses -- the 55mm f2 and 50mm f1.9 -- are "multi-coated" in some way, by some definition ("features a unique combination coating"), although maybe not the same as other DSB lenses.
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on Dec 28, 2020 14:45:05 GMT
Posted: Dec 28, 2020 14:45:05 GMT
I hope this doesn't come across as a bubble buster. Using the word "combination" as a means of describing lenses and coatings seems to be marketing-speak more than anything else - however - as telling as it might seem to be, it might not mean there's anything unique for a specific lens. All DSB lenses may very well have "combination" coatings, but without knowing the individual details on each lens model, and every lens element within it, it may not be possible to identify if one lens model - or lens element - is special. Unfortunately, the sales document writers had to come up with descriptive terms to sell products, and even when true, they're usually word tricks to add value where none exists. "Combination" might mean a few things when it comes to photographic lens coatings. There's basically 2 types of overall coatings... with AR (anti-reflective) coatings, and HR (highly reflective) coatings; where each type can have multiple ways of applying the coatings (with some ways being far more expensive than the others). In effect, it's possible to have a combination of combinations, all in the same lens's optical diagram. Add to that the multiple glass compositions possible with each lens element (ED or LD, Flint, Crown,etc.) and there's a whole new set of combinations to multiply the results by. One lens might have 6 elements, with 2 types of glass, 2 'flavors' of AR coatings (i.e., 2 different types of oxides), with 2 different coating application types (ion beam, and plasma)... and still technically be a single coated lens (1 coating per element), but at the same time, it could also be a "combination" coating when taken as a whole. Another lens in the same family might have 1 glass type throughout, and only 1 coating type and application style; and end up being the traditional single coating lens type we usually assume that to mean. DSB lenses in general, might be some mix of simple single-coated and/or "combination" coated lenses. My knowledge of chemsitry is sub-par, and where it crosses over into photography it's something I've tried to understand a little better over the last few years. A few bookmarked references to boggle the mind if anyone's up for a deep dive: Edmund Scientific article, on lens coatings: www.edmundoptics.com/knowledge-center/application-notes/lasers/an-introduction-to-optical-coatings/A blog on understanding lens designs, by a working optical designer - on different designs and coatings: www.pencilofrays.com/lens-design-forms/A History of the photographic lens (pg. 16, on anti-reflective coatings): www.google.com/books/edition/A_History_of_the_Photographic_Lens/IaBXn06OlWsC?hl=en&gbpv=1 |
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