I'm cross posting this from another forum. It had been a discussion of
analog LCD monitor clarity, and had drifted into a disucssion of
Cleartype. But the real reason that I'm posting it is for the
information on analog LCD monitor dot clock adjustment, and the link to
the [free] alignment test pattern generator program:
*********
What cleartype does is take the sharp black to white edge transitions
that a printed character or font naturally has (that I and the font
designer would agree that it is supposed to have), and intentionally add
grey halftones in the transition areas between black and white.
On analog LCDs THAT ARE IMPERFECTLY ADJUSTED, where the "transition"
from black to white may be subjet to jitter between two adjacent pixels,
this may be subjectively desireable -- by "fuzzing up" the transition so
that the jitter becomes less objectionable.
On digital LCDs with DVI interfaces (which includes all notebooks, by
the way), and on PROPERLY ADJUSTED (with a test pattern) analog LCDs,
the transition doesn't "jitter" to begin with, so in that sense this is
not necessary, although some people may still find this subjectively
better, while others find it subjectively and/or artistically hideous.
In the end, since cleartype can be turned on or off, users can view it
both ways and make up their own mind. In all cases, however, I think
that it is just plain dumb to apply cleartype without FIRST getting an
appropriate test pattern and correctly adjusting the display dot clock.
Cleartype, even for people who might find it subjectively attractive,
is largely a band-aid to "mask" imperfect mapping of the pixels on the
LCD display to those generated in the video card. Before applying the
band-aid, it's certainly worth taking the time to get the monitor
properly adjusted, because in most cases you CAN achieve perfect mapping
that, whether you prefer cleartype or not, eliminates "pixel jitter" and
moire distortion entirely.
[The required test pattern is a series of alternating black and white
vertical bars, one single pixel wide, across the entire screen. A
program that will produce this is available free at:
http://www.winsite.com/bin/Info?500000030936
This program is variously known as CRTAT, CRTAT2, and CRT Align
(crtalign), and was written by Stephen Jenkins in about 1992 or 1993.
To use the program for this purpose, after installation, select the
leftmost of the 3 functions in the "Test" group and then check both
check-boxes. This is a very old Windows 3.1 program written in visual
basic. It runs under XP just fine, absolutely perfectly in fact, even
with today's high resolution monitors (you do need VBRUN300.DLL, which
it may or may not come with depending on where you download it from, but
if you don't have it, it can be found on the web). This program is
totally non-invasive, it's "installation" makes NO changes to your
registry or to ANY system components or files. In fact, if you just
unzip the program and double click the exe file, it will run fine
without actual "installation" (but the program and the help file need to
be in the same directory, and VBRUN300.DLL needs to be available).
When you display this pattern, you should see an absolutely perfect and
uniform field of alternating (but very, very fine) black and white
vertical bars. If you see "moire" distortion, or smearing, your display
isn't adjusted correctly. Digital monitors (with DVI interfaces) will
always be "perfect". Analog monitors will usually show an initial moire
distortion pattern until they are adjusted (dot clock frequency and
phase). In most cases, perfect adjustment can be achieved (and is
"remembered" by the display), but in some cases you can't achieve this.
If you have an analog monitor and you don't use this program to adjust
your monitor, you are doing yourself a real disservice.]
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