W3C home > Mailing lists > Public > www-style@w3.org > November 1996

Re: Relative weight - reader vs. author styles

From: Chris Lilley <Chris.Lilley@sophia.inria.fr>
Date: Mon, 25 Nov 1996 16:49:02 +0100 (MET)
Message-Id: <9611251649.ZM3752@grommit.inria.fr>
To: "David Perrell" <davidp@earthlink.net>, "Chris Lilley" <Chris.Lilley@sophia.inria.fr>, "www-style" <www-style@w3.org>
On Sep 10,  6:42am, David Perrell wrote:

> Chris Lilley wrote:
> > A guess - you don't use a Mac or an SGI or a NeXT to browse with.
>
> Right.
>
> > Another guess - the doument authors did. And it wasn't illegible to
> > them. The difference being gamma correction, ignoring which causes
> > errors of several hundred percent - especially for dark colors.
>
> May be. Or attempted subtlety by PC users with CRT brightness cranked
> to maximum.

Changing the brightness alters the slope of the transfer curve, it doesn't
alter curvature.


> > Note that the CSS1 specification defines what a color means, in
> > terms of measurable objective color specifications, and also that
> > the minimum that implementors must do to display these tightly
> > specified colors is to implement reasonable gamma correction.

> How does sRGB help without an opsys-level CMS or sRGB-compliant
> display?

Firstly, it helps by defining what the colors mean, precisely. So it then
becomes a question of closeness of approach to an objective standard, rather
than differeing and equally valid interpretations.

Secondly, the defined gamma curve "happens" to be what a dumb PC uses
anyway so no gamma correction is required for Wintel PCs. Ditto for
the majority of Unix workstations and X terminals.

It isn't what is used by default on a Mac and it isn't what is used by
default on an SGI. But MacOS "happens" to have a CMS built in and an API to
alter the lookup table; and Irix (>=6.2) also "happens" to have a CMS built
in (and can display different windows with different gamma values, too).

So for minimal implementation, the two platforms that need to do any
processing are the two platforms that can readilly do that processing.
This was not an accident.

> Is there any progress in getting display hardware mfgr's to
> buy into this?

It seems so. Similarly for printer manufacturers. And W3C is tracking the
issue of color rendering on the Web.


-- 
Chris Lilley, W3C                          [ http://www.w3.org/ ]
Graphics and Fonts Guy            The World Wide Web Consortium
http://www.w3.org/people/chris/              INRIA,  Projet W3C
chris@w3.org                       2004 Rt des Lucioles / BP 93
+33 (0)4 93 65 79 87       06902 Sophia Antipolis Cedex, France
Received on Monday, 25 November 1996 10:49:16 GMT

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