Projection screens are generally divided into two types based on their functionalities: reflection projection screen and broadcast projection screen. It can also be divided into a soft and hard screen base depending on the materials they are made from.
Home theater generally uses a soft reflection screen. My brother-in-law originally wanted to buy a ¥ 1000 (~ $ 150) “import screen”, but a friend of his who sells projection screens told him that it is difficult today (in China) to distinguish the authenticity of an import screen, it’s difficult even for him. Some of those labeled ‘import’ or ‘joint capital’ were actually made somewhere in southern China. He felt that he would rather buy a ¥ 300 domestically made 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 the screens in the local market are made from high-profit Bolivian beads that are used to project newspaper clips, they are just not suitable for the video frequency.
In theory, a white wall with a smooth side is actually the best “screen”. Because its gain is 1, which means that the projected light can be fully reflected, which is an ideal “no absorption, no gain” state. Unfortunately, for the purpose of absorbing and proliferating the sound wave, he already made the wall a back wall with sound absorbing material and installed plywood. Making it impossible for it to serve as a “projection screen,” he had to find another solution.
You may be wondering at this point: why do people still bother buying expensive screens when we can all use white walls?
Well, there are always benefits and advantages of using a professional screen: convenient, artistically beautiful and dignified, a good screen can also compensate for the insufficiency of a projector and improve the visual effect. Among the expensive screens, one type is the “gray screen” (it costs around ¥ 15,000, roughly $ 2000). This type of screen was probably originally designed for liquid crystal projectors. The biggest problem with the liquid crystal projector is that the color appears dark and gray, insufficiently calm. This is your “birth defect” which is caused by your liquid crystal board and the path of the rays.
Regarding the gray screen, we all know that gray is simply a lighter black and that black absorbs all visible light. Gray can only partially absorb visible light, it is as if the brightness of the image is reduced. If you have used the “brightness / contrast gradient” option of any image processing software, you should surely have noticed such a phenomenon that reducing the brightness is equivalent to increasing the contrast gradient. Same concept, since the brightness has been reduced, in turn its contrast gradient increased. The black effect is enhanced due to the higher contrast. We can also experience the same effect when we look through the sun visor of our car. In fact, there are many ways to reduce the brightness, it is not necessary to use the gray screen. There are magazines that recommend putting the light gray filter of a photographic camera to the projection lens, the principle is the same. You can even use a simpler method, that is, you need to adjust the projector’s output brightness or increase the contrast gradient. You don’t need to spend a penny, you can achieve a similar effect, but the premise is that the showroom should be dark enough.
Going back to the bottom line, if a gray projector screen costs you $ 2000, it’s definitely not just because the screen color changes from white to gray. Speaking from the optical principle, I am afraid there is much more behind it. I assume that certain chemical compositions have probably been added to the screen material that changed the intensity of reflection or absorption of different wavelengths of light, thus changing the brightness and contrast gradient of the entire image, which is the innate defect. . of liquid crystal board after all. Besides this, what other tricks do you think they can play? It does not seem possible with the little knowledge of physics that I have.
It seems rather to include 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. If I have to buy a ¥ 15,000 screen, then it would just work better if I rallied the money and bought a top-tier ¥ 30,000 projector to achieve a better effect without any extra effort. A 15,000 yen screen is an incredible price for my brother-in-law (imagine his monthly income is only 3,000 yen). Also, if you buy a name-brand Japanese gray screen, you are actually spending most of the money to pay for labor that you are personally uncomfortable with.
The ideal screen for the DLP projector my brother in law bought should be like a white wall, just let the light from the project fully reflect without any “reservations”. He thought he really didn’t need such an expensive screen. So he finally decided to make one of his own.
Exactly how did he do it? You may not believe how simple and inexpensive it really was! You spent a little over ¥ 10 (about $ 1.50) at a home decor store on a faint grain self-adhesive pure white matte formica PVC panel, cut to the right size, glued to your original background wall, that is , flat and smooth! With such a PVC screen, you don’t need to worry about the ‘curl’ phenomenon that can happen to a normal projector screen after about 12 years of use, you also don’t have to worry that it will one day turn yellow. due to natural oxidation. But remember that it requires some gluing techniques to make it work perfectly for you. The result? Excellent!
Here are a couple of self-made projector screen photos of my brother-in-law as ‘evidence’:
http://www.news-blogs.com/_images/entertainment/diy_screen.jpg
http://www.news-blogs.com/_images/entertainment/diy_screen2.jpg
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