Kodak anistigmat lens 21 1/4 inch f11 - f128

[David Flockhart]

Can't seem to find much info about this lens in the archives. It covers my 8x20 and must have been a copy lens as the printing on the front is reversed. SN is: ER299. It is a barrel lens. It works well and that's enough, but I'm curious about how old it might be and the type of lens it is. Thanks in advance for your thoughts.

[Richard Knoppow]

The two letter prefix of the serial number is a date code for the last two numbers of the year. The key word is CAMEROSITY for the numbers 1,2,3,4, etc. ER is 1945. The reversed printing and speed suggest its a process lens. Process lenses were often used with reversing prisms to eliminate the need to float off the emulsion and reverse it, otherwise necessary for half-tone and line work. My guess is that this is a four element air spaced lens of the type known as a dialyte. This is the same basic form as the Goerz Artar and many other lenses. Kodak built an enormous number of lenses of this type. The smaller ones are numbered with 70 series numbers. The higher the number the longer the focal length. Kodak Anastigmats were also made in a 30 series, which are Tessars. The lens is probably not an apochromat but its likely very well corrected. The very small f/stops are also a sign of its being a process lens. In half-tone work there is a relationship between the screen pitch, distance, magnification and stop in order to get the best quality dots. So, the aperture must cover a wide range. Many process lenses also have slots for Waterhouse stops or filters.