From: Michael Geary (Mike_at_Geary.com)
Date: Wed Sep 01 1999 - 13:51:45 EDT
This sure generated a lot of discussion! <g>
One amusing thing: Once you know how an LCD panel is made, with repeated
columns of red, green, and blue, your original question actually has a
visual illustration of the phenomenon right in the question itself...
> Can anyone with a 600E try this out? I have a 2645-5AU so anything similar
> would be cool.
>
> Change the background colour in Windows 98 to the color
> (R,G,B)=(256,0,256), which is magenta. Now look at the left and right
> edges of the screen. Is the last pixel (on the left) red or (on the right)
> blue? That's what I get. If so, what is the reason for this?
Since it happens that the subpixels in an LCD screen are arranged in RGB
order, look at that (R,G,B)=(256,0,256). This gives you a column of red, a
column of black, and a column of blue, repeated across the screen.
So the leftmost subpixel column is red, followed by a column of black. Then
you have adjacent blue and red columns, which blend visually into magenta as
you expect. The pattern repeats across the screen, ending with a column of
black and a column of blue.
Because the leftmost red column and the rightmost blue column each have a
black column next to them, your eye picks them out as separate colors.
You can see a related effect on many Web pages, at least in Internet
Explorer. With a typical link color of blue and a "hover" link color of red,
when you roll the mouse over a link, you not only see the color change to
red, but you can see the text shift to the left a tiny amount. Roll the
mouse back and forth over the link and you'll see the text shift left and
right.
This happens for the same reason: When the link is blue, the rightmost
subpixel of each triplet is on. When it changes to red, the *leftmost*
subpixel is on instead. So the entire text shifts to the left by two
subpixels, or 2/3 of a pixel--enough to notice fairly easily.
Microsoft's ClearType technology (also discovered independently by other
people) takes advantage of this by using "subpixel rendering"--using the
knowledge of the R,G,B column arrangement to position text more precisely in
the horizontal direction.
Steve Gibson has a very interesting description of this and a demo program
at:
http://www.grc.com/freeandclear.htm
-Mike
ThinkPads in the Open Directory: http://geary.com/thinkpad/
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