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 ¥150,000 screen if your projector cost
you ¥15,000. 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 which he
personally doesn’t feel comfortable.
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 self-made projector screen photos from my brother-in-law
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Jacklyn Chen- Webmaster of news blogs and a full time mom who works very hard to make living with multiple web
sites. For more information and articles about home theater, visit the Home Theater Blog , or check out the Entertainment Blog [http://entertainment.news-blogs.com]
for more entertainment related information.
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