In addition to the diagrams shown here, there is additional technical information.

The Ektra's Ektar lenses, like most other lenses of this period were heavily influenced by the Tessar design and were created from designs and with manufacturing technology Kodak had developed in the 30s. While the formulae used were not novel, their implementation in the Ektar line was generally excellent for the period. Quality control in the Kodak manufacturing process was considered outstanding.

The f/3.5 50mm is a standard Tessar type with four elements in three groups, with the last elements reversed in power from the original Tessar design. The f/3.5 90mm is a simplified version with three separate elements. The longest manufactured lens in the series, the f/4.5 153mm, has a double negative cemented pair behind the stop. The f/3.8 135mm uses a differently designed rear element, which may have been an original Kodak design. The f/3.5 35mm is a Heliar design by F. E. Altman of five elements in three groups, very similar to the f/3.5 100mm Ektar used on the Medalist. Apparently Kodak had planned a super tele of about 250mm, since the variable viewfinder has a setting for 254mm. Neither the glossy Ektra prospectus, published on the camera's release in 1941, nor the "Kodak Lenses" section of the Kodak Reference Manual, published originally in 1942, have any mention of this long lens, though I have heard unsubstantiated claims that there was at least one prototype. The f/1.9 50mm is a variation of the Biotar design, originally used in the f/2.0 45mm Ektar mounted on the Bantam Special. Of these lenses, the f/3.5 50mm and f/3.5 35mm are reputed to be the sharpest, with the f/1.9 50mm to have the poorest resolution and flare performance, a characteristic of most highspeed lenses of that period. All Ektra lenses attach to the body with a screw mount that locks when snug. Two keyways on the mount make lens orientation a no-brainer with the body in any position.

While Kodak had begun treating air-glass surfaces in the late 30s. In material published for the Kodak Ektra, Kodak Medalist and Kodak Eastman Ektar 14" Kodak included statements like: "inner surfaces of the lenses are treated by a coating process that improves the clarity and brilliance of the negatives obtained." I can only find documented evidence of their widespread use of their Lumenized coating of magnesium fluoride in lens manufacture of the late in mid-1946. The Kodak publication Kodak Lenses and Shutters (1939), lens sections of the Kodak Reference Handbooks , printed in 1940 through 1945 do not include Lumenized lenses., while the An updated version of the Reference Handbook, published as one of the first separate Kodak Data Books in mid-1946 first introduces the term,"Lumenized". Kodak Lenses, Shutters and Portra Lenses, 3rd Edition (1948) describes the process, but no longer includes the Ektra lenses.

We have since learnd from Rudolf Kingslake's 1951 book, Lenses in Photography, that these first inner coatings were of calcium fluroide. Kingslake had become the Director of Optical Design for Kodak, and supervised these first coating operatins as well as the experimentation with deposition and baking of alternative fluroide coatings. Magnesium fluroide was eventually selected as the best hardcoating and was applied variously to Kodak lenses through the war years. This was eventually extended to all lens lines and was identified company-wide as Lumenizing in 1946. Whether later Ektra Ektars ever had this coating is for me an open question. Most lenses that are hard-coated or 'Lumenized' will have an symbol following the lens serial number, but there are early exceptions. I have not seen an Ektra Ektar later than EO (1946). Unlike other Ektars with serial numbers stamped in the lens ring, Ektra Ektar serial numbers were stamped in the metal shank of the lens barrel that is inserted into the camera body lens mount. While I have seen late model Ektra Ektars with reflections that appeared to suggest hard-coating, none had the circled L preceding or following the serial number. Without comparing an early model with a late model of the same lens, I'd be hesitant to say that the later one was hard-coated. So all Ektra Ektars were coated, but many with calcium fluoride only on inner surfaces, presenting a significant problem to restorers. I would not disassemble Ektra lenses to clean their inner surfaces; some technicians may know how to do this without damaging the soft coating, but I would get this specific assurance before authorizing such work and I would specifically prohibit such work when I was having maintenance work done on such lenses unless this assurance was given. More general information on Ektar lenses is available  , and from a page no longer available, but restored from Robert Monaghan's Medium format site  .

Kodak also manufactured and distributed lenses for broadcast and industrial cameras. In some cases, Television Ektanons appear to be similar to Ektra Ektars lenses but may have different lens formulae and coatings; the focusing mechanisms may also differ.

  Ektar Lenses
.Ektra Basics ..Ektra II/Values

Kodak Ektra - The Prospectus (ca 1941) How to Use the Kodak Ektra (1945)  
Prices Kodak Ektra, its lenses, accessories and related products
January 1941
Kodak Ektra Registration Card (ca 1945)  
Contemporary correspondance about the Ektra Scans of pages in Kodak publications relating to the Ektra  

Patent application for Kodak Ektra shutter
    Ektra Internals  


10/19/2010 12:58