Re: Color Visibility

Len,

Thanks for your comments. I'll incorporate them in version 2. Please send the color selections when you get a minute.

Chris

-----Original Message-----
From: Leonard R. Kasday <kasday@acm.org>
To: Chris Ridpath <chris.ridpath@utoronto.ca>; WAI ER IG List <w3c-wai-er-ig@w3.org>
Date: May 18, 1999 1:54 PM
Subject: Re: Color Visibility


    Thanks Chris
    
    That looks like a good way to do it. Here's some quick feedback:
    
    - feedback form should be users's default colors or they wouldn't be able to read it <grin>.
    
    - need instructions to make sure user isn't overriding the colors
    
    - Also ask what type of computer and display they are using:
    
    Mac
    PC with MS-DOS
    PC win 3.1
    PC windows 95 or 98
    Unix
    
    The reason for asking is that in practice different operating systems have different "gamma", which relates screen luminance L to R G or B value 
    
    Red Luminance = R^gamma etc.
    
    Of course, there's no inherent reason that operating systsem would have to be different. Historically, the Mac did a "gamma correction" that gives subjectively better color rendering and typical PC's omitted it.
    
    Actually, there are some PC video cards that also do gamma correction, but if we ask people what video cards they have it's gonna be harder to get a good response.
    
    - for same reason ask
    
    CRT
    LCD
    
    cause these also have different gamma.
    
    With LCD's gamma varies with the angle you view the screen, but lets not worry about that.
    
    
    - Be interesting to find out if person has presbyopia, i.e. the inability to refocus that takes place as we get older (after the age of around 45), that makes people need reading glasses. This compounds problem of seeing red and blue on dark background because the eye has chromatic abberration, so these colors are a bit out of focus for a person sitting at a distance comfortable for black on white.
    
    
    This will also correlate with whether they have the normal age-related loss of sensitivity to blue.
    
    How do we find out? Could ask if they use reading glasses. But people who aren't presbyopic, but are just farsighted, would also say yes. Well, we can't get too complicated. Just a question as to whether they use reading glasses is probably enough.
    
    Hmmm. Maybe we really want to put those questions at the END. Just ask for their email address in in the beginning.
    
    
    Next, I'll get you a selection of colors that are relatively uniformly distributed in color space and that are "Netscape safe"
    
    Len
    
    
    
    At 11:56 AM 5/18/99 -0400, Chris Ridpath wrote: 
    >>>>
    
        We've been looking at the problem of trying to determine what colors are good/bad for web page visibility. As part of the process, we wanted to set up a web site where people could go and 'vote' on several different color combinations. In this way we would get some real world results. Our example site is at: http://aprompt.snow.utoronto.ca/ColorTest.html Please take a look and let me know your comments. I also have a small program the tries to determine whether colors are good/bad visibility for use in web pages. Let me know if you'd like to have a look at it. Chris 
        
    
    
    
    
    -------
    Leonard R. Kasday, Ph.D.
    Universal Design Engineer, Institute on Disabilities/UAP, and
    Adjunct Professor, Electrical Engineering
    Temple University
    
    Ritter Hall Annex, Room 423, Philadelphia, PA 19122
    kasday@acm.org 
    (215} 204-2247 (voice)
    (800) 750-7428 (TTY)