Message-Id: <mailto:199607301244.HAA15782@library.wustl.edu> Date: Tue, 30 Jul 1996 14:39:52 +0200 From: Rudolf Gschwind <mailto:Mgschwind@FOTO.CHEMIE.UNIBAS.CH> Subject: Re: color negatives To: Multiple recipients of list IMAGELIB
>Greetings,
>
>I've been told that NO scanner can successfully scan color negatives. Does
>anyone have any experience refuting this claim?
>
>Victoria Yturralde
>Photo Archivist
>CA Dept. of Parks & Recreation
>Victoria Yturralde
>Photographic Archivist
>Calif. Dept. of Parks & Recreation
The reason, why scanning of color negatives makes problems, can be explained only by photography. Normal color scanners have a spectral sensitivity, which matches more or less the visual eye sensitivity, i.e., the peak sensitivities at 450, 560 and 610(!) nm. This gives you good results in scanning originals or slides. Color negative material on the other hand have color dyes with different absorptions. The "cyan" dye has its absorption maximum at 700 nm, i.e. already in the near infrared. (consequently, the color negative printing papers are senitized in the red to this wavelengths). That means, a color scanner does not see "enough" the cyan dye. A second reason is the strong orange colored mask of negative materials. This color mask absorbs strongly the blue light. The problem is , that the CCD element in the scanner has its maximum light sensitivity in the red and NOT in the blue region, i.e., thereis not enough blue light,which makes problems for blue colors.
R. Gschwind (http://foto.chemie.unibas.ch)