Kingslake's accounts are probably as authoritative as any we are likely to see published and those are circumspect in the chronology of developments through the early 1940s of Kodak's coating procedures. Product brochures and reference publications establish that softcoating was added to the premium models of lenses about 1941-- the 14-inch Eastman Ektar for large format cameras, the Ektars for the Ektra, the 100mm Ektar for the original Medalist and the companion 105mm f /3.5 Heliar for small press cameras. Kodak's printed materials for these products mention either lens coating for inner surfaces or a process that reduces reflections. There is no general discussion of lens coating in the lens section of the Kodak Reference Handbook, 1940 or 1942-45 editions. The Data Book: Kodak Lenses Shutters and Rangefinders:For Revising Kodak Reference Handbook, © 1942, 1945, Second 1946 Printing contains the first discussion of the Lumenizing process and the branding mark in these publications. The July 1946 number of Kodak Handbook-Notebook News list a 4-page article, KODAK LUMENIZED LENSES, ANTI-REFLECTION COATING.

Kodak may have been discrete in describing its early lens coating technologies because it was experimenting with hard coating from roughly 1940 through 1945. Kodak produced cameras, lenses, sighting devices and rangefinders for the U. S. Army and Navy during WWII and perhaps tried different coatings for different applications. It is possible that not all of the Kodak production lines were updated with the capability of using coated lens elements at the same time. While war-time advertisting was clearly anticipating the postwar consumer market -- for example, in this Medalist ad -- fixing the end date of the war would have been guesswork and revealing information about things like the coatings on Aero Ektars was likely prohibited.

Based on Richard Knoppow's pre-2000 inquiry with Kodak , Kodak records of when they started applying coatings to their lenses were no longer accessible. The collection of Kodak papers at the University of Rochester might hold some information about lens coating practices during this period. Michael Briggs has examined a reasonably large sample of military Aero Ektars, some as early as 1941, and found that all but one were coated, though not marked with the characteristic .

While the table below is anything but a comprehensive registry of Kodak lenses, I have asked for and many visitors have responded with information about Kodak lenses of this period. That has been helpful in trying to fill in the gaps about early 1940s coatings. As of August 2010, there doesn't seem to be a reason to update this table with data for hardcoated lenses marked from 1946 onwards, nor for uncoated lenses manufactured before 1945. The following lenses are of still of interest in establishing Kodak lens coating practices:

• Lenses marked with before 1946
• Coated unmarked lenses before 1946
• Ektra Ektars of any age that appear to be hardcoated
• Kodak lenses with the pre-CAMEROSITY numbering scheme that appear to be coated.
• Kodak professional lenses made after 1965, to define Kodak's last contribution to this market
  

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While later lenses will have an obvious color tint in the glass, determining whether coating is present is sometimes difficult with early lenses, often because these lenses have fewer optical surfaces on which the coating is applied. Those involved in Kodak's early coating process would have known how to differentiate the appearance of uncoated, calcium fluroide-coated and magnesium fluroide-coated glass; the rest of us have to rely on inference. EY Ektra Ektars almost certainly would have had calcium fluroide-coated glass. They are pretty indistinguishable from ER Ektra Ektars, which may have been hardcoated, and more obviously coated than more modest mid-40s lenses that are Lumenized. Uncoated lenses will have no colored refections off different optical surfaces when a light sources is reflected at an oblique angle, whereas the light source reflected off different surfaces of a coated lens will appear in slightly different colors. Different light sources can affect appearance.

Kodak Ektars from 1946 through 1965 were single-coated; and it is possible that some Ektars after 1965 were multi-coated, though Kodak's offerings in the prosumer market by this point were a trickle. Kodak AG lens production followed Kodak's U. S. conventions; coated lenses were marked with ; it is possible, but not very likely that late model Retinas may have been multi-coated. Generally, the additional coating layers in multi-coated lenses are designed to filter out reflections at wave lengths not filtered by a single coating. About 1970, lens makers began the strategic application of six or seven coatings that filter most frequencies of visible light. The greater the number of air/glass surfaces, the greater the need for effective coating. Multicoating of modern lenses with many elements, particularly zoom lenses, is essential to maintain good contrast. For the kinds of formulas used for most Ektars, multicoating would make only a marginal contribution to flare reduction and then primarily in color.

Kodak research showed that lens baffle design was as important as lens coating in reducing lens reflections that decreased contrast, so cameras designed in the late 1930s and throughout the 1940-50s had improved baffles and paint materials.

Additional information about the history of lens coating and a large collection of posts about lens coatings.

DATA ON SELECTED KODAK LENSES
1935-1965

Lenses are ordered by Kodak brand, then by length. All shutters for Anastigmat Special/Anastar and Ektar lenses are mounted in Kodak Supermatic or Flash Supermatic shutters unless otherwise marked according to the legend in the footnotes.

Coated

0 - EI 1630¶
('48)

Ektar 50mm f/1.9 (Ektra) EFP

Coated

• Visible differences between uncoated, softcoated and hardcoated Kodak lenses were relatively subtle between 1940 and 1965 when compared to the appearance of modern multi-coated lenses, but some differences in coloration of reflections should be noticeable.
• While hardcoating of Kodak lenses may have begun as early as 1940, this wasn't generally discussed in public documents until 1946, when the term Lumenizing emerged.
• Regardless of the presence of hardcoating in a growing fraction of advanced amateur and professional lenses from 1941 through 1945, few had the Lumenizing mark before 1945.
• The only collector reporting any pattern in hardcoating prior to 1946 is Michael Briggs, a collector of Aero Ektars, who has noticed that most were hardcoated. Some elements have a yellowish-brown color, which he suggests may have become that color over time due to radioactive properties in some of the glasses used. Some of this coloration may have been intended to increase haze reduction in these aerial lenses.
• All Ektra Ektars, the Ektars in Medalists, the Ektars in Bantam Specials made after about 1940, and large format Eastman Ektars made after about 1940, at a minimum, had soft calcium fluoride coating applied to inner surfaces. When harder fluroides were introduced to particular models, these would have replaced calcium fluoride.
• The single example of an Ektra Ektar made on or after 1946 was not hard coated. Ektra Owners: More data would obviously be useful. The serial numbers on Ektra Ektars are not on the lens ring, but are stamped in the metal on the shank of the lens that is placed in the camera's lens mount. So far it isn't clear whether Kodak embossed the on hardcoated Ektra Ektars.
• How were the serial numbers assigned? Sequentially by year or sequentially by lens model? Given the relatively high serial numbers of some lenses, and that Kodak probably wanted a unique number on each lens, it appears to me that a single annual sequence was used. To have assigned numbers by model, would have produced many duplicate numbers and made public use of these as identifying numbers very confusing. If lens rings were produced in a single shop, they likely would have been produced in batches. Perhaps, if the shop were going to make 50 rings for 80mm WF Ektars, they took the last number used and started their run from that point. If production was more dispersed or done in parallel operations, perhaps they assigned ranges of numbers based on projected production. Note the close proximity of numbers in many cases for lenses of the same type and year. An experienced Ektra collector has developed some hypotheses about Kodak serial numbering   .

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