Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site peora.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!whuxl!houxm!vax135!petsd!peora!jer From: jer@peora.UUCP (J. Eric Roskos) Newsgroups: net.rec.photo Subject: Re: Product Quality: Color prints from slides Message-ID: <1750@peora.UUCP> Date: Sat, 26-Oct-85 21:41:15 EST Article-I.D.: peora.1750 Posted: Sat Oct 26 21:41:15 1985 Date-Received: Mon, 28-Oct-85 03:28:13 EST References: <298@tekig4.UUCP> <349@vaxwaller.UUCP> <5746@tekecs.UUCP> Organization: Perkin-Elmer SDC, Orlando, Fl. Lines: 51 > Reversal color print processes are not as good as negative print > processes. MY OPINION: Don't bother to flame if you disagree! Why would anybody flame you! :-) After all, it's true... Color rendition in prints from color negatives is better than the color rendition in prints from slides. This is because present-day dyes have "tails" on their spectral absorption curves that overlap the spectrally-absorptive regions of the other dyes. This is particularly a problem for the cyan layer, and to a lesser degree, the magenta layer. The result of this effect is a color "impurity" in the negative image, typically a red impurity in the cyan areas, and a yellow impurity in the magenta areas. To correct for this, color negative films have a yellow and a red color mask whose color is decomposed in proportion to the presence of the corresponding impurity. Thus in an area with a large yellow impurity, the yellow mask will be almost completely decomposed, i.e., the yellow mask goes away, to be replaced by the yellow impurity. Likewise for red. The result is that the film has a uniform yellow-red cast to it, rather than having a red cast in the cyan areas and a yellow cast in the magenta. However, with slide films, this can't be done, since the slide is intended to be viewed by projection, and a yellow+red cast (well, possibly the complementary colors for a reversal film) would be unacceptable, whereas when printing from a negative this can be corrected with color correction filters. Thus, so that the whites will be white on a slide, the other colors have to be compromised slightly in the print. This is why color negative films exist. (Well, also because the processes to develop them are simpler.) Contrary to popular opinion fostered by the fact that photojournalists and others who intend their photographs to be reproduced by ink printing use slides (and the biased editorial position of some popular photography magazines), the color rendition of color negative films is "truer" than for slide films. It should seem intuitively probable that a film that is *designed* for making prints would be better-optimized for making good prints than a film that was designed for making slides which are occasionally printed. On the other hand, grain is marginally better in Kodachrome. It's my personal feeling that image sharpness is not sufficiently good with 35mm cameras to make that much of a fuss over grain (eventhough I do use a very fine-grain B&W film myself!) when comparing an ASA 100 film with Kodachrome, and they don't make Kodachrome for larger-format cameras. -- Shyy-Anzr: J. Eric Roskos UUCP: Ofc: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer Home: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jerpc!jer US Mail: MS 795; Perkin-Elmer SDC; 2486 Sand Lake Road, Orlando, FL 32809-7642