This Retina-Curtagon 28mm f/4 from Schneider was one of my most hated focal lengths in the beginning, but has since become a very frequently used lens, which apart from its known advantages is that it can be used with a focus barrel. At the same time, the macro effect is very good. At the same time, by converting the DKL to m42 and then connecting the focusing barrel, the shooting distance of this lens can be from infinity to several centimeters. There are many six-group lens groups, one of which is a cemented lens, that is, seven elements in six groups), but the common problem of this lens is that there are internal scratches in the lens.

The Schneider-Kreuznach Retina-Curtagon 28mm f/4 lens was the first lens to be used on the Kodak retina SLR Type 034, the Type 034 Retina Reflex S introduced in 1959 as a redesigned version of the original Retina Reflex. The main difference is that it uses a fully interchangeable lens, the same lens used on the Kodak Retina IIIS rangefinder camera. The lens mount is usually called the Deckel mount, which is also commonly known as the DKL lens, but it should be noted that the DKL lens used by Kodak cameras and the DKL lens used by Voigtlander cameras are different, although the conversion to digital cameras is universal. transfer ring. But in fact the mount of the film machine is different. This lens can be used on Retina Reflex S, III, IV, Instamatic Reflex and Retina IIIS camera bodies.

Source: https://web.archive.org/web/20121006003750/http://www.kodak.com/global/en/consumer/products/techInfo/aa13/aa13.pdf

Schneider Kreuznach (German pronunciation: [ˌʃnaɪdɐ ˈkʁɔʏtsnax]) is the abbreviation for the company Jos. Schneider Optische Werke GmbH, and is sometimes referred to simply as Schneider. They are manufacturers of industrial and photographic optics. The company was founded on January 18, 1913 by Joseph Schneider as Optische Anstalt Jos. Schneider & Co. in Bad Kreuznach, Germany. The company changed its name to Jos. Schneider & Co., Optische Werke, Kreuznach in 1922 and in 1998 to the present name of Jos. Schneider Optische Werke GmbH. Schneider’s detailed history can be found in the article before the poison lens.