Homemade projector screen: the principle and how to do it yourself

Projector screens are generally divided into two types based on their functionalities: reflection projector screen and transmission projector screen. It can also be divided into soft and hard screen base based on the materials they are made of.

Home theater generally uses a smooth reflection screen. My brother-in-law originally wanted to buy a so-called “import screen” for ¥1000 (~$150), but a friend of his who sells projection screens told him that nowadays (in China) it’s hard to tell the authenticity of an import screen , it is difficult even for himself. Some of the ones 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 a good feeling than buy this kind of “import screen”. What this friend said makes a lot of sense. But after doing some research, my brother-in-law discovered that all the screens in the local market are made of high-gain Bolivian beads used to project newspaper clips, they are just not suitable for the video frequency.

Theoretically speaking, a white wall with one smooth side is actually the best “screen”. Because its gain is 1, which means that the projected light can be completely reflected, which is an ideal “no absorption, no gain” state of being. Unfortunately, in order to absorb and propagate 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 “projector screen”, he had to find another solution.

You may be wondering at this point: why do people still bother buying 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, a good screen can also make up for the inadequacy of a projector and enhance the visual effect. Among the expensive screens, one type is the “grey screen” (costs about ¥15,000, about $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 plate and the path of the rays.

Regarding the gray screen, we all know that gray is simply a lighter black and 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, surely you should have noticed such a phenomenon that reducing the brightness is equivalent to increasing the contrast gradient. Same concept, since the brightness has been reduced, this in turn increases its contrast gradient. The black effect is enhanced due to the higher contrast. We can also experience the same effect when looking through the sun visor glass of our car. In fact, there are many ways to reduce brightness, you don’t have to use a gray screen. There are magazines that recommend putting the light gray filter of a photographic camera on the projection lens, the principle is the same. You can even use a simpler method, i.e. you need to adjust the output brightness of the projector or increase the contrast gradient. It is not necessary to spend a hundred, you can achieve the same effect, but the premise is that the showroom must be dark enough.

Going back to the bottom line, if a gray projector screen is costing you $2000, it’s definitely not just because the color of the screen changes from white to gray. Speaking from the optical principle, I am afraid that there is much more behind it. My guess is that there were probably certain chemical compositions 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, that constitutes the defect. innate. liquid crystal board after all. Besides this, what other tricks do you think they can play? It doesn’t seem possible with what little knowledge of physics I have.

Sounds more like throwing 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. If I have to buy a ¥15,000 screen, it would just work better if I pooled the money and bought a higher level ¥30,000 projector to achieve a better effect without any extra effort. A ¥15,000 screen is a crazy price for my brother-in-law (imagine his monthly income is only ¥3,000). Also, if you buy a brand name Japanese gray screen, you will actually be spending most of the money to pay for work that you personally are not comfortable with.

The ideal screen for the DLP projector my brother-in-law bought should be like a white wall, just letting the light from the project reflect completely without any “reserves.” He thought he really didn’t need such an expensive screen. So he finally decided to make one on his own.

Exactly how did you 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 matte pure white Formica PVC self-adhesive panel with faint grains, cut to the right size, glued to your original background wall, that it’s all flat and smooth. ! With such a PVC screen, you don’t need to worry about the ‘curving’ phenomenon that may occur on a normal projector screen after about 12 years of use, and you also don’t need to worry about it turning yellow one day. 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 photos of the projector screen taken by 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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