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Projector screens are generally divided into two types base on
their functionalities: reflection projector screen and
transmission projector screen. It can be also divided into soft
and hard screen base on the materials they are made from.
Home theater generally uses soft reflection screen. My
brother-in-law originally wanted to buy a ¥1000 (~$150)
so-called "import screen", but a friend of his who sells
projector screens told him that it is hard nowadays (in China)
to distinguish the genuineness of an import screen, it is hard
even for himself. Some of them that are labeled with 'import' or
'joint capital' were actually manufactured somewhere in the
south of China. He felt that he'd rather to buy a ¥300
domestically manufactured screen with good feelings than buy
this kind of "import screen". What this friend said makes
perfect sense. But after doing some research, my brother-in-law
found that all screens on the local market are made from high
gain Bolivian bead that is used for projecting newspaper clips,
they are simply not suitable for video frequency.
Theoretically speaking, a white wall with one smooth side
actually is the best "screen". Because its gain is 1, meaning
that the light projected can be completely reflected out, which
is an ideal state of being "no absorption, no gain".
Unfortunately, for the purpose of absorbing and proliferating
the sound wave, he already made the wall a background wall with
sound-absorbing material and plywood installed. making it
impossible to serve as a "projector screen', he had to find
another solution.
You might be wondering at this point: why do people still bother
purchasing expensive screens if we can all use white walls?
Well, there are always benefits and advantages of using a
professional screen: convenient, artistically beautiful and
dignified, good screen can also make up the insufficiency of a
projector and improve visual effect. Among the expensive
screens, one type is "gray screen" (cost about ¥15,000, roughly
$2000). This kind of screen probably was originally designed for
liquid crystal projectors. The biggest problem with liquid
crystal projector is that the color appears dark and grey,
insufficiently calm. This is its "congenital defect" that is
caused by its liquid crystal board and path of rays.
Regarding gray screen, we all know that gray is merely a lighter
black, and black absorbs all visible light. Gray can only
partially absorb visible light, it is like brightness of the
picture is reduced. If you have used any picture processing
software's "brightness / contrast gradient" option, you should
certainly have noticed such phenomenon that reducing brightness
is equivalent to increasing contrast gradient? Same concept,
since the brightness has been reduced, it in turn increased its
contrast gradient. The black effect gets improved due to the
bigger contrast. We can also experience the same effect when we
look out through the sunshade glass of our car. In fact, there
are many ways to just reduce the brightness, you don't have to
use gray screen. There are magazines recommending putting the
light gray filter of a photographic camera to the projection
lens, the principle is the same. You can even use more simpler
method, namely you need to adjust the projector's output
brightness or increase the contrast gradient. No need to spend a
cent, you may achieve the similar effect, but the premise is
that showroom must be dark enough.
Back to the bottom line, if a gray projector screen cost you
$2000, definitely it is not just because the screen color is
changed from white to gray. Speaking from the optical principle,
I'm afraid there's a lot more behind. I'm guessing probably
certain chemical compositions have been added to the material of
the screen that changed the reflection or absorption intensity
of different wavelength of light, thus changed the luster and
the contrast gradient of the entire image, that, makes up the
inborn flaw of liquid crystal board after all. In addition to
this, what other tricks do you think they can play? It doesn't
seem to be possible with the meager knowledge of physics that I
have.
It sounds more like it to throw in a ¥15,000 screen if your
projector cost you ¥150,000. But adding a ¥15,000 screen to a
¥15,000 projector doesn't make much sense at all. If I have to
buy a ¥15,000 screen, then it would simply work better if I put
the money together and buy a ¥30,000 higher level projector to
achieve better effect without any extra effort. A ¥15,000 screen
is a crazy price to my brother-in-law (imagine his monthly
income is merely ¥3000). Also if he buys a name brand Japanese
gray screen, then he actually spend most of the money to pay for
the labor.
The ideal screen for the DLP projector that my brother-in-law
purchased should be like a white wall, just let the project
light reflected completely without any "reservation". He figured
that he really didn't need such costly screen. So he finally
decided to make one on his own.
Exactly how did he do it? You may not believe how simple and
inexpensive it really was! He spent a bit over ¥10 (about $1.50)
in a home decorating store on a self-adhesive pure white matted
formica PVC panel with dim grains, cut the right size, pasted to
his original background wall, that is it, flat and smooth! With
such PVC screen, he doesn't need to worry about the 'curl-up'
phenomenon that may occur to a regular projector screen after
around 12 years of use, he also doesn't need to worry that it
would turn yellow one day due to natural oxidation. But remember
it requires some pasting techniques to make it work perfectly
for you. The result? Great! Here are couple of photos from him as
'evidence'.
Note: You may freely republish this recipe as long as author bio
and active hyperlinks are kept intact. Thank you.
About the author:
Jacklyn Chen - A webmaster and full time mom who works hard to
make living with multiple web sites. For more information and
articles about home theater, visit Home Theater Blog, to see the entire
entertainment blog, visit http://entertainment.n
ews-blogs.com.
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