Understanding the documentation of Kodak lenses and shutters during the period covered by this site--the mid-1930s through the mid-1950s--depends on an understanding of a publishing convention that Kodak adopted in 1940, a 5 1/2 x 8 1/2 page format with an extra quarter-inch added to the width for 17 ring-binder holes that engaged a special loose-leaf binder.

A site visitor has shared a photocopy of Data Book Kodak Lenses, Rangefinders and Shutters For Revising Kodak Reference Handbook, © 1942, 1945, Second 1946 Printing. This appears to be one of the first Data Books--of the minor variation sort. Most of its contents are the same as that of the 1945 loose-leaf version of the Reference Handbook, section 1, "Kodak Lenses, Rangefinders and Shutters", with these exceptions:

• This is the first time, in the end user materials I have studied, that Kodak describes its process of hard coating and consistently uses the term "Lumenized". Previously, Kodak included sentences like, "The inner air-glass surfaces are treated by a special process which reduces reflections." in the descriptions of individual lenses to describe a soft coating of calcium fluoride. In the 1940 edition of the Kodak Reference Handbook none of the lenses were so described. In the 1942, 1945 edition, the Ektra Ektars, the Bantam Special and Medalist Ektars and the 8 1/2-, 10-, 12- and 14-in Eastman Ektars have the "inner coating" note; the f /3.7 105mm, f /4.5 101mm and f /4.7 127mm unmounted Ektars have no mention of coating.

"LUMENIZED"* LENSES

The most recent advance in Kodak lenses in the wide application of Lumenizing. Many Kodak lenses now bear a thin, hard coating of magnesium fluoride to reduce surface reflections and consequently flare light and spots. Picture quality is improved in shadow contrast and detail and in shadow color purity of color pictures. Because of the reduced tendency to veiling and spots, the camera has greater freedom of position with regard to the sun or bright lights.

Lumenizing slightly increases sd the speed of a lens having many glass-air surfaces. More light is transmitted to the highlights, less to the shadows. In color work the increase may amount to as much as a third of a lens opening setting; in bland-and-white no allowance should be made.

When all the elements including condensers of a projections systems are Lumenized, screen brightness is increased--50% in the case of the Kodaslide Projector, Model 2A. The projected picture quality is also improved, mostly in the shadows.

Lumenized enlarger lenses tend to give improved highlight detail, especially from negatives of high contrast of large shadow areas.

Lumenized lenses, as currently made, bear a circled "L" engraved on the mount. Treated lenses can also be identified by the slight tint seen by reflected light. The lens is uncolored by transmitted light. Color rendering is not affected.

Dirt on Lumenized lenses tends to cancel the advantages of Lumenizing. Oil spots look like holes the surface. Lumenized lenses can and should be cleaned in the usual way, as described elsewhere.

Recently designed Ektar lenses have mechanical improvements in the mount, also designed to reduce flare light.

*T. M. Reg. U. S. Pat . Off.

Source: Data Book Kodak Lenses, Rangefinders and Shutters For Revising Kodak Reference Handbook, © 1942, 1945, Second 1946 Printing