Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!elroy.jpl.nasa.gov!jarthur!ucivax!orion.oac.uci.edu!biivax.dp.beckman.com!falstaff.css.beckman.com!heffron From: heffron@falstaff.css.beckman.com (Matt Heffron) Newsgroups: comp.graphics Subject: Re: Psycho Graphics Message-ID: Date: 28 Feb 91 17:11:18 GMT References: <91Feb20.131305est.6899@neat.cs.toronto.edu> Reply-To: heffron@falstaff.css.beckman.com Organization: Scientific Services, Beckman Instruments, Inc. Lines: 61 Nntp-Posting-Host: falstaff.css.beckman.com In <91Feb20.131305est.6899@neat.cs.toronto.edu> mgreen@cs.toronto.edu (Marc Green) writes: >>From: euaneg@eua.ericsson.se (Nils-Erik.Gustafsson) >>Not to be nit-picking, but it's not quite as bad as 1/6 (17%). >>The literature seems to agree upon 6-8% (almost all having a >>green/red-deficiency). >> >>Nils-Erik (Gustafsson) >>ELLEMTEL Telecom Systems Lab >It's not that simple. It depends on whether you are talking about the >truly "color blind" (dichromats and monochromats, who are missing a >pigment or two) or merely color anomalous (trichromats who have all >three pigments but with reduced amount or shifts in spectral >sensitivity). The 6-8% number includes the anomalous trichromats, I >believe. So the real number of color blind people is really quite >small. To make life more complicated, color-blinds fall into two >groups (and a rare third group). >However, it is also a mistake to think that females are never color >blind. The last I looked, there was a lot of research saying that >females who carry the gene for color blindness often have mixed >patches of normal and abnormal retina. They may pass crude color >screenings (like Ishihara) but still do not have normal color vision. >In short, attempts to take color blindness into account when creating >visual displays is probably hopeless. There are too few people and >they fall into too many different groups, each of which would require >different modifications. However, you CAN try and be aware of the common cases and deal with them, instead of just assuming it's hopeless! For example, as Nils-Erik Gustafsson pointed out, most of the color anomalous cases, are red/green deficient (me for one). It isn't hard to make sure that when you have a choice of colors for some things, that you try to avoid putting similar intensity reds, greens, and browns together, or putting low intensity reds, greens, and browns with black (or even near very dark blue). I just saw a marketing program (developed for another division of Beckman under contract) which "highlighted" the letter of a command by displaying it in dark red instead of black! It took me several looks to figure out the color discrimination required to see which key to press! (I'm going to inform the division that had the program done, that they have a problem!) In general, it's not too hard to cover the common cases. Here are a couple of guidelines that I use for color selection. - When possible, use contrast instead of color for differentiation. - Avoid dark reds, greens, and browns. Lighter shades seem to be easier to discriminate (at least for me). - Try not to use a set of the same (or similar) colors in multiple combinations. (We had a programmer here whose color vision was ENTIRELY differential. I once showed him an orange object in front of a beige wall and he correctly said it was orange, when I moved it in front of a medium red chair, he said that it now appeared GREEN!) -- Matt Heffron heffron@falstaff.css.beckman.com Beckman Instruments, Inc. voice: (714) 961-3128 2500 N. Harbor Blvd. MS X-11, Fullerton, CA 92634-3100 Cute saying/disclaimer in development.