Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!ames!elroy!aero!venera.isi.edu!raveling
From: raveling@vaxb.isi.edu (Paul Raveling)
Newsgroups: comp.windows.x
Subject: Re: Luminance from RGB
Message-ID: <6797@venera.isi.edu>
Date: 15 Nov 88 19:56:06 GMT
References: <8811132229.AA02726@dawn.steinmetz.GE.COM>
Sender: news@venera.isi.edu
Reply-To: raveling@vaxb.isi.edu (Paul Raveling)
Organization: USC-Information Sciences Institute
Lines: 24

In article <8811132229.AA02726@dawn.steinmetz.GE.COM> stpeters@dawn.UUCP writes:
>
>Our visual system appears to assign color based on ratios of the
>inputs - and on its own biases.  It is an ornery system indeed and is
>quite willing to reject input that does not fit: ...

	A demonstration of this that I used to do with our filled-vector
	map graphics involved changing the ocean color.  Starting
	with a seemingly well-saturated chocolate brown for land
	and dark blue for water, I'd change only the water color.
	Going to light blue made the land suddenly appear black.
	Holding something over the screen to mask out water areas
	showed that the land, in fact, was still the same "vivid"
	chocolate brown.

	This was a fairly radical difference in perceived color
	and luminance.  An "accurate" model of perception would need
	to incorporate info about graphic context of the color
	in question.


---------------------
Paul Raveling
Raveling@vaxb.isi.edu