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Understanding
LCD and DLP
An LCD device creates the image by shining a bright light
through either one, or more usually three, LCD panels - these are
rectangular arrays of pixels which can be made to go dark, transparent, or
any state in between. The picture is formed by controlling the transparency
of each of these pixels. In a 3-panel device, each panel creates the red,
the green, and blue components of the image which are then merged optically
to create a full color image, which is then projected through a lens. The
number of pixels per panel depends on the device. The Sony VW10HT, for
example, has a million pixels in each panel. During manufacture, if an LCD
crystal itself, or the tiny transistor that drives it, fails, you get a bad
pixel. If it's permanently transparent, you get a bright pinprick on your
screen. If it's permanently dark you won't see it.
DLP devices work similarly, except that, instead of light shining through
LCD arrays, the light is reflected off an array of tiny mirrors. These tiny
mirrors are tilted to give anywhere between full brightness (the mirror
reflects the light straight into the lens) and full darkness (the mirror
reflects the light away from the lens) and anywhere in between. DLP arrays
are expensive. As a consequence, all "normal" DLP projectors only have one
DLP array. The color image is created by sequentially energizing the array
with the red, then green, then blue components (maybe not in this order).
Synchronized with this is a colored wheel that spins in front of the array.
So, when the blue component of the image is on the array, at the same time,
a blue filter is in front of the array. So, the picture projected is,
actually, all blue, all green, then all red. All this happens so quickly
that your brain merges the three colors into a full color image.
DLP gives better black levels than LCD because you're not trying to shine a
bright light through something dark - LCDs never can go completely opaque -
whereas DLPs can easily reflect the light fully away from the lens. BUT -
with single-chip DLP's you can, sometimes, see the effect of the sequential
colours - manifests itself as rainbow effects around fast moving objects (or
if you scan your eyes across the screen).
Also, nobody makes a true 16x9 DLP chip. So all DLPs are intrinsically 4x3 -
which means that, for the majority of DVDs which are wider than 4x3, you're
"wasting" resolution in black bands top and bottom. Most LCDs are also 4x3.
However, the Sony VPL-VW10HT has 16x9 LCD arrays which make better use of
the available pixels to produce your picture.
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