I believe that LCDs using Twisted Nematic (TN) based panels are the ones
that allow light to pass through in their unpowered state. This means that
a completely "dead" pixel (with all three sub-pixels affected) will appear
as a white spot on your screen. With the other types of panels, In-Plane
Switching (IPS), Multidomain Vertical Alignment, (MVA), and Patterned
Vertical Alignment (PVA), a completely dead pixel will appear as a black
spot.
Manufacturers often don't tell you what sort of panel is being used in their
LCDs (which often varies from model to model). Generally, the less
expensive LCDs and ones that are advertising the lowest response times are
using TN panels. However, there now are some IPS and PVA/MVA panels
advertising low gray to gray response times, which are using some electronic
trickery to speed up what otherwise would be sluggish response times for
small color shade transitions.
You can recognize a TN panel by its narrow vertical viewing angle. If you
view the monitor from below straight on, it quickly darkens, and if you view
the monitor from an angle above straight on, it washes out. Although LCD
monitor specifications are notoriously misleading, often you can pick out
the TN panels because they list a narrower vertical viewing angle than their
listed horizontal viewing angle (though some manufacturers fudge this, so
equal viewing angles do not mean you aren't dealing with a TN panel).
It is a bit harder to distinguish a VA from a IPS panel. Your best bet is
to try to find a review of other website that lists what panels are being
used in which LCDs. Samsung, for example, makes their own panels. The PVA
panels are exclusively their technology, and most of their higher end LCDs
use this kind of panel. However, they sell these to other manufacturers;
so, PVA panels may end up under other brand names. Samsung also makes TN
panels, which can be found in both their LCDs and those of others.
A few LCD resources:
http://www.xbitlabs.com/articles/other/display/lcd-guide.html (probably more
than you want to know, but the last part of the article covers the
differences between the various kinds of panels)
http://www.flatpanels.dk/panels.php (you can search for characteristics of
LCDs in their database)
http://forums.anandtech.com/messageview.aspx?catid=31&threadid=1745344&enterthread=y
(a quick overview of LCD technology as well as discussion of some currently
popular models)
Given how expensive a good LCD monitor can be relative to the total cost of
a computer system, how important the monitor is to determining what kind of
computer experience you are going to have, and how long people will continue
to use a good monitor, it is surprising to me how difficult it is to find
really good reviews of this particular computer component. As a result,
many consumers are stuck not really finding out what the strengths and
weaknesses of their new LCD are, until they get it home and have been using
it for a while, doing various kinds of computer related tasks.
John Sproule
----- Original Message -----
From: "David Jonathan Justman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, May 22, 2006 12:41 AM
Subject: [PCBUILD] LCD Question
I am now the proud owner of an LCD display, and know almost nothing about
them. First question: I read somewhere on the Web that the pixels on some
LCDs are black when in their unpowered, passive state, and that other are
white in their unpowered passive state. How do I know which mine is?
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