xkaes
18-Jun-2017, 11:07
I've read with interest this old thread about lens coating which included much about the history and evolution of lens coatings. It also uncovers how the terms used for "coatings" have evolved.
http://www.largeformatphotography.info/forum/showthread.php?128214-When-did-coating-of-large-format-lenses-begin/page3&highlight=coating
The coatings of Japanese lenses (as opposed to Japanese cameras with German lenses) appears to have occurred after WWII. Supposedly, Minolta was the first Japanese lens manufacturer to produce coated lenses -- a single coat in 1946 (the Semi IIIa era). I assume it was a layer of magnesium fluoride, but that doesn't mean that all of the elements and all sides of all elements were coated. Fuji lenses, at least their large format ones, started to get a coating around 1954. Again, I assume it was a single layer of magnesium fluoride. In 1958, Minolta pioneered its "Achromatic coating" which was two layers of magnesium fluoride deposited in different thicknesses. I have no details if this means two layers of different thicknesses on the same glass surface or two different layers on two different surfaces. They were using the term "Achromatic coating" well into the 1970's on lenses that were obviously multi-coated with different minerals. Each of Fuji's and Minolta's lens coatings (and undoubtedly everyone else) changed with their new series of lenses (ex. Minolta's Rokkor, Auto-Rokkor, Rokkor-X, Yashica's ML, MC, DX, and Fuji's SW, SWD, W, NW, CM-W), but there is plenty of evidence that the coatings changed/improved even within the same series.
But is begs the question, "What consitutes multi-coating?" Minolta had lenses with two coats of magnesium fluoride. They didn't call it multi-coating, but it seems that it qualifies. On their enlarging lens spec sheets, they lists some some coatings as "amber", and others as "amber and magenta", but none as "multi coated". "amber and magenta" are obviously at least two coatings, but the "amber" lenses might have been more than one layer, too.
At some point, Minolta started to use the word "multi-coated". Fuji called their approach EBC (electorn beam coating). Tamron BBAR (Broad-Band Anti-Reflection) coating -- up to seven layers on glass-to-air surfaces. Most people would think that all lens elements get the same treatment/coating. To me, all this means is that SOME elements of all of these multi-(more than one)-coated lenses may have a lot of coatings, but others may have only one layer (or perhaps none?).
I've had the Fujinon f5.6 105mm EBC in the NW and CM-W. The NW version appeared multi-coated on the front and single-coated on the rear, while the CM-W version appears multi-coated on both. I'm not surprised since they are different optical designs. The same with my Fujinon f5.6 75mm EBC SWD -- it appears multi-coated on the front and single-coated on the rear. Some Carl Zeiss T* lenses have little multi-coating.
So it appears that "multi-coated" is apparently a very loose term. Sometimes lenses that have quite a lot of multi-coating are not labeled as multi-coated, but some that are labeled multi-coated have limited multi-coating.
Multi-coating -- More than one coating on any surface? More than one coating on more than one surface? More that one type of mineral?
http://www.largeformatphotography.info/forum/showthread.php?128214-When-did-coating-of-large-format-lenses-begin/page3&highlight=coating
The coatings of Japanese lenses (as opposed to Japanese cameras with German lenses) appears to have occurred after WWII. Supposedly, Minolta was the first Japanese lens manufacturer to produce coated lenses -- a single coat in 1946 (the Semi IIIa era). I assume it was a layer of magnesium fluoride, but that doesn't mean that all of the elements and all sides of all elements were coated. Fuji lenses, at least their large format ones, started to get a coating around 1954. Again, I assume it was a single layer of magnesium fluoride. In 1958, Minolta pioneered its "Achromatic coating" which was two layers of magnesium fluoride deposited in different thicknesses. I have no details if this means two layers of different thicknesses on the same glass surface or two different layers on two different surfaces. They were using the term "Achromatic coating" well into the 1970's on lenses that were obviously multi-coated with different minerals. Each of Fuji's and Minolta's lens coatings (and undoubtedly everyone else) changed with their new series of lenses (ex. Minolta's Rokkor, Auto-Rokkor, Rokkor-X, Yashica's ML, MC, DX, and Fuji's SW, SWD, W, NW, CM-W), but there is plenty of evidence that the coatings changed/improved even within the same series.
But is begs the question, "What consitutes multi-coating?" Minolta had lenses with two coats of magnesium fluoride. They didn't call it multi-coating, but it seems that it qualifies. On their enlarging lens spec sheets, they lists some some coatings as "amber", and others as "amber and magenta", but none as "multi coated". "amber and magenta" are obviously at least two coatings, but the "amber" lenses might have been more than one layer, too.
At some point, Minolta started to use the word "multi-coated". Fuji called their approach EBC (electorn beam coating). Tamron BBAR (Broad-Band Anti-Reflection) coating -- up to seven layers on glass-to-air surfaces. Most people would think that all lens elements get the same treatment/coating. To me, all this means is that SOME elements of all of these multi-(more than one)-coated lenses may have a lot of coatings, but others may have only one layer (or perhaps none?).
I've had the Fujinon f5.6 105mm EBC in the NW and CM-W. The NW version appeared multi-coated on the front and single-coated on the rear, while the CM-W version appears multi-coated on both. I'm not surprised since they are different optical designs. The same with my Fujinon f5.6 75mm EBC SWD -- it appears multi-coated on the front and single-coated on the rear. Some Carl Zeiss T* lenses have little multi-coating.
So it appears that "multi-coated" is apparently a very loose term. Sometimes lenses that have quite a lot of multi-coating are not labeled as multi-coated, but some that are labeled multi-coated have limited multi-coating.
Multi-coating -- More than one coating on any surface? More than one coating on more than one surface? More that one type of mineral?