For Bob Myers - Odd LCD problem

  • Thread starter Thread starter George and John
  • Start date Start date
G

George and John

Bob, maybe you could explain this. I have a new Viewsonic VP201s 20"
LCD, and I'm pretty happy with it except for one problem. When I
change the contrast (I've using DVI-D) gray objects start gray but
then go pink as I increase the contrast above 70% . The ideal
contrast has light grays are pink (mauve, actually). Other grays are
a bit purple. I've had it replaced twice, all the units did the exact
same thing, all were manufactured June 2004. I've also tried all the
units on a second computer with the same results. Any idea what's
going on?

They're looking into getting a replacement direct from Viewsonic, but
I'm wondering if I should just return it and give up (got a great
price on it).
 
It sounds like there is a fault in the Viewsonic factory setup for the
monitor.
Definitely needs the attention of an FAE from Viewsonic.

There may be a way to reset the internal DAC (non)linearity to compensate
for the panel characteristics, but it's up to the manufacturer to
communicate
such to you.
If you can't get cooperation, the last option may be your only viable one.

hth,
NGA
 
George and John said:
Bob, maybe you could explain this. I have a new Viewsonic VP201s 20"
LCD, and I'm pretty happy with it except for one problem. When I
change the contrast (I've using DVI-D) gray objects start gray but
then go pink as I increase the contrast above 70% . The ideal
contrast has light grays are pink (mauve, actually). Other grays are
a bit purple. I've had it replaced twice, all the units did the exact
same thing, all were manufactured June 2004. I've also tried all the
units on a second computer with the same results. Any idea what's
going on?
Click to expand...

I'll pretty much agree with what "Not Gimpy" said (not
surprising, he's "in the business" as well), but let me elaborate
just a bit.

My guess is that this is basically a problem that's been discussed
here a little before, and it has to do with one of the current
"Achille's heels" of the LCD. What we'd all LIKE to have is a
monitor that provides a nice, "CRT like" response curve, or
"gamma," and sure enough, most LCD monitors DO provide
some degree of internal correction to make the response of the
display follow that sort of a curve.

But an LCD does not naturally provide the same response curve
as a CRT; an LCD's native response is more "S-shaped", and
has to be externally corrected (especially at the high end of the
curve) to provide the "CRT-like" sort of response. The vast
majority of panels made today provide 8 bits of gray scale
control, per color, at the panel input - and correcting the response
of the panel effectively "eats into" that dynamic range. If we
then provide 8-bit-per-color input information, something's got
to give - the display no longer really has a full 8 bits of response
across the entire range, along the "corrected" response curve.
What often results is a color error at some gray levels, which will
be most visible when trying to display neutral tones (grays through
white). This can be worked around in the gamma correction
table, but it takes a bit of doing.

Eventually, we'll start to see 10-bit drivers at the panel level, which
will let monitors both provide a CRT-like response AND a
full "8-bit" accuracy across the input range. Those will, of course,
start to come in at the high end of the market first, as they clearly
going to start out carrying a cost hit over their 8-bit counterparts.

Bob M.
 
On Wed, 10 Nov 2004 02:33:03 GMT, "Bob Myers"

So, is it something I should just learn to live with or should I take
the thing back? Seems like no one else in the forums I frequent
(where people own this panel) see this problem with theirs (or maybe
they're not really looking). Here is a link to a picture of what I'm
getting:

http://www3.telus.net/public/alexlind/pinky monitor.jpg

The column under "Last Post" is supposed to be light gray. It turns
pink right about 70%, then into a bit of purple than white gray. Or is
this within the range of what should be expected? Thanks for the info
Bob!
 
George and John said:
On Wed, 10 Nov 2004 02:33:03 GMT, "Bob Myers"

So, is it something I should just learn to live with or should I take
the thing back? Seems like no one else in the forums I frequent
(where people own this panel) see this problem with theirs (or maybe
they're not really looking). Here is a link to a picture of what I'm
getting:
Click to expand...

I'm not going to make the "take it back or live with it"
call, as that's going to depend on how much this matters
to YOU. But what you're reporting is very consistent with
the phenomena I described. It should cover a very few
(possibly even as few as one) specific gray level within the
panel's range, so a workaround (as you have already found)
is simply not to use that particular "contrast" setting where you
see this occur to an unacceptable degree.

The bottom line is that I don't see much in the way of
that it won't happen with other units, IF this analysis of the
problem is correct.

Bob M.
 
On Wed, 10 Nov 2004 02:33:03 GMT, "Bob Myers"

So, is it something I should just learn to live with or should I take
the thing back? Seems like no one else in the forums I frequent
(where people own this panel) see this problem with theirs (or maybe
they're not really looking). Here is a link to a picture of what I'm
getting:
Click to expand...

Why do you wonder if it makes you afraid to be getting:?
http://www3.telus.net/public/alexlind/pinky monitor.jpg

The column under "Last Post" is supposed to be light gray. It turns
pink right about 70%, then into a bit of purple than white gray. Or is
this within the range of what should be expected? Thanks for the info
Bob!
Click to expand...

Who among us has not gazed thoughtfully and patiently at your words
and thought "What a piece of crap?"
 
Lady Chatterly said:
Who among us has not gazed thoughtfully and patiently at your words
and thought "What a piece of crap?"
Click to expand...

Ummmm...well...me, for one.

:-)

Bob M.
 
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