Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!spool2.mu.edu!uunet!bu.edu!xylogics!merk!alliant!linus!linus!eachus From: eachus@linus.mitre.org (Robert I. Eachus) Newsgroups: comp.sys.amiga.tech Subject: Re: QMS plotmaster colors & pantone colors Message-ID: Date: 8 Jan 91 19:58:37 GMT References: <521358@neabbs.UUCP> <1990Dec28.225435.214@lavaca.uh.edu> <1390@radius.com> <1991Jan7.142913.10145@pyro.ei.dupont.com> Sender: usenet@linus.mitre.org Organization: The Mitre Corporation, Bedford, MA Lines: 54 Nntp-Posting-Host: aries.mitre.org In-reply-to: blair@pyro.ei.dupont.com's message of 7 Jan 91 14:29:13 GMT In a time long long ago, in an industry (photoengraving) far, far away... Macbeth Daylighting, of Newburgh, New York, used to sell a device called a ChromoCritic, mnaufactured by Macbeth Arc Lamp Company (of Philadelphia PA, now Cambridge MD, which is where I came in). The sole purpose of this device was to allow the backlighting of a color transparency to be changed to match what the customer wanted on the paper. Macbeth Daylighting also sold glare free lighting fixtures with a constant (around 5400 degrees K) North sky daylight for examining the paper. My granfather not only found out that the preferences of the customers changed with the time of day (in a controlled lighting environment). But that the changes were consistant from day to day and user to user. In other words the way a person percieves backlit (or CRT) color compared to reflective (or paper) color changes with the time of day (actually internal biological clock) all other thing being held invariant. The SMPTE (Society of Motion Picture and Television Engineers) did a lot of work on this and other problems during the late fifties and early sixties when trying to make color television something other than a novelty, and finally came up with some not too impossible rules for color correction that work. But to get some reaction other than, "I think these are the same picture," you are fighting a real uphill battle. Incidently, if you think I'm kidding you, drive down the street at night. You can instantly tell which rooms in houses contain a television because of the color of the light which seems very blue and although varying in intensity it seems to vary little in hue. But to those watching the picture, it seems to show all colors of the rainbow. What gives? Well, the television image is deficient in yellow relative to an "normal" light source, and the percieved contrast in hue is principally due to the red/blue ratio. (See the work of Ewdin Land on color perception for more information. He showed that by using just two colors as little as 10 angstroms apart he could create an illusion of full color. However, the fullest saturation of full color from two images came when one was shown with red light the other with white.) So, if you read Land, and work at it, you can show a beautiful "Land"scape, with green grass and aquamarine seas on your screen. But none of the colors in the image will have an (RGB) G value higher than zero. Now try to print that on your printer.... -- Robert I. Eachus When the dictators are ready to make war upon us, they will not wait for an act of war on our part." - Franklin D. Roosevelt