Archived posting to the Leica Users Group, 2006/03/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]From: "subminiature" <subminiature@ntlworld.com> Subject: Carl Zeiss news on Spur 400 lp/mm on film http://www.zeiss.de/C12567A8003B58B9/?Open Then select Camera Lens News 24 Latest Newsletter Issue, February 2006 Gourmet Food for ZEISS IKON A camera system capable of extraordinary resolving power asks for adequate image recording media ... Resolving Power Record with ZEISS Biogon T* 2,8/25 ZM "The high resolution film of choice was the SPUR Orthopan UR supplied and processed by SPUR. The result was a whopping 400 lp/mm on film, recorded with the Biogon 25 at f/4 in the center of the image. This value, 400 lp/mm, corresponds to the maximum resolution theoretically possible at f/4; in other words it represents the calculated "diffraction limited" performance at this aperture. It is noteworthy that this test was conducted with a production lens on a production camera, indicating that the film was precisely positioned and flat." -------- This figure is astounding and has the same relevance to ordinary photography as deep sea diving has to splashing around in the pool. Extraordinary resolving power, at near the maximum theoretical limit, has been possible for some time using monochromatic light and lenses computed for the specific object and image distances. Some are used in photolithography in manufacturing computer chips, others in spy satellites. But if you read the full text you will find that this resolution is available only in the center of the field with special ASA 25 emulsions. According to the Kodak catalog, film usable for general photography has a maximum resolving power of 125 lp/mm or lower. Most of us also enjoy taking pictures of multicolored three dimensional objects at varying distances and find the esthetics of flat resolution charts to be lacking. But I suppose it makes good advertizing copy. I wonder what the bokeh of the Zeiss lens is. Larry Z