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Paulo last won the day on November 28 2014

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  1. I couldn't have said it better. Thank you. That is another one of the reasons why it's better to use the wall supports. They make it easier to place the screens in any position. About the height at which the screens are placed, there is a lot of people lost in this matter. The chairs in movie theaters are designed to force us to sit more of less upright. But at home things are different. If I am an older man I tend to recline more than if I am a young person. The couch I am using also influences my sitting position, some are more comfortable if I'm sitting upright, others feel more comfortable when I am lying down. In this last case, the ideal position for the screen would be the ceiling. So, how do we find the best position for the screen? First of all forget the rules/measurements that you find on the Internet written by people that sometimes know less about this than you. Sit on your couch, in the position that you think you will be using the longest (usually the most comfortable position for that couch). Look at the wall without focusing on any specific part of it. Notice the part of the wall where your eyes will naturally rest. If necessary, move your head around a bit and then try once again to find that part of the wall. Mark the position on the wall where your eyes are focusing (the point you found on 4). That should be the center of your screen. Better than using rigid rules that don't take into account a lot of different things, find the position that is more comfortable for you. If you already have a certain age, that would be the position where in the middle of the movie you close your eyes and start snoring.
  2. @Nebrium These screens are made with many layers. Some of them are not big enough to create a screen with 300cm x 170cm. There is a possibility: We can make seams. Horizontal seams, near the bottom in order to disturb as less as possible. The 4 outermost layers are big enough, so no cuts there. But I can't guarantee that the seams underneath will be invisible. @xano "Axis" is English for "axe" in French. It is an invisible line perpendicular to the center of the screen. If you look at the first image again, it is the line that separates angle A from angle B: A distance of 3,5m between the projector and the screen is too little. You will see some "hotspot" effect in the more uniform images. If you can place it further away from the screen, it will be better. (You can also turn the projector 180 degrees, place a good mirror in front of it to reflect the light back to the screen and that should give you a little more distance.) It is always a good idea to use the wall supports supplied with the screens.
  3. If you tilt the projector, the image will go outside the screen. Next you will have to use, for example, lens-shift to place the image back on the screen. The end result is almost the same as not having done anything. So, this doesn't work. However, the geometry of the image (keystone) will have changed. So, this is a good way to adjust the keystone "manually" when the projector doesn't have that function (like the Sanyo Z-2000 I'm using). If anyone thinks is necessary, I can explain this in more detail. Tilting the screen using our supplied wall supports is a very simple and fast process. But if you really must have the screen vertical on the wall, there are other ways to correct the viewing angle. Everyone knows that when a billiards' ball hits the edge of the table at an angle, it is "reflected" back in the same angle. In the image above the angle A is the same as the angle B. If you think of the projector's light as a billiards' ball, this second image will feel familiar. Now let's imagine we put the projector closer to the screen, from position 1 to position 2. What happens now is that the light that hits the screen is being reflected to a lower position than before (D). There are 2 ways to correct this while keeping the screen vertical: We can lower the projector to position 3, which, as you can see above, is equivalent to having the projector back at position 1. Another way is raising the screen a little to try to find the correct angle again (from B to B'): In my modest opinion, using the wall supports for orienting the screen is not only easier, but also quicker and more effective.
  4. Here is a simple way to measure the gain of a screen. First of all I’d like to give you a notion of how screen gain is measured in a laboratory. In position A we place a sample of a standard white (magnesium oxide) material. In position F we place a light source. In position B we place a semi-reflector glass. In position S we place a sensor. After calibrating the sensor, the sample A is replaced with the material we want to measure. The light is sent from the source F, goes through the half-mirror B and hits the sample A. The light emitted from the sample is reflected in the half-mirror B and hits the sensor that measures the value that will be used to calculate the gain of the sample by comparison with the standard white material that was measured before. After knowing the gain of the sample (angle 0), the sensor will be moved vertically, horizontally or in another direction, making several measurements until we find the angle where the gain is half of the one we measured at 0 degrees. Why half of the initial gain? There are several reasons for this but where it concerns projection screens it’s mainly for us to have a notion of how how the screen diffuses the light (the viewing angle of the screen). As a curiosity, our brain easily accepts an image with variations of up to 50% brightness between the middle and the edges of the screen. It is also curious to know that it is possible to make it so that 2 cloths with different gains (for instance one with gain 1 and another with gain 1,5 or one with gain 1 and another with gain 0,5) appear to have the exact same gain. A more detailed explanation can be given later if interest arises. Back to the simple measurement. An untrained eye will have difficulty distinguishing a screen with gain 0,9 from a screen with gain 1 when observed in different situations. But when observed on top of one another using small samples, a gain difference of 0.1 is perfectly noticeable. We will use a very old Sanyo Z-2000 because right now we don’t have other projectors available. Nowadays people have easy access to catalogs, of multiple brands, with samples of scenic material, gauges for laboratories and, most importantly for us right now, samples of image projection screens. All with registered brightness gains (and other things). One of the reasons why no one supplies samples of technical screens is because, similar to a camera, where the lens has many optical elements, a technical screen also has many layers. Each technical screen is usually manufactured as a whole piece (there are also screens being marketed as technical that really are not). (I can say that the Lusoscreen Home-Cinema Darkstar Flat has a total of 9 layers.) In this case, I am purposefully going to choose the Da-Lite samples because it is an old, international and credible manufacturer of normal projection screens. We start by cutting out a sample with known gain of 1. Then we orient the screen so that, when we sit on the couch, we can see the top of the projected image with the same brightness as the bottom of that image. If the screen has a spot effect, try to put it at the center. If you can’t see the spot effect, try to take photos with your phone. Usually it’s easier to see these things in digital photos. Next we place our gain 1 sample in the center of the screen. This allows us to immediately see whether the screen has a gain greater or lower than 1. Naturally, if the screen is brighter than this sample is because it has a gain greater than 1 and vice-versa. Since the screen seems to have a gain slightly below 1, we’ll see what happens when we place the sample to the side of the projected image: Please note that it’s much easier to see the differences in the photos, than when using our eyes. Next we’ll use a sample with a gain of, for example, 0,8 and we repeat the observation: In this case we can see that the Lusoscreen Home-Cinema Darkstar Flat is brighter than the sample of 0.8 gain so, at the center, this screen has a gain much higher than 0,8. Next we move the sample to the side of the screen and we observe again. Here in the side, the gain of the screen is still greater than 0,8. We can now conclude that the entire surface of the screen has a gain greater than 0,8. And since we saw with the previous sample that the screen’s gain is smaller than 1, it’s easy to conclude that the gain of this screen is between 0,8 and 1 in all of its surface. Is it necessary to be more precise with our measurements? In my opinion, no. Having a screen with 8,6~8,7 gain or with 9,2~9,4 gain in practice is all the same, because there are many other factors to consider that are equally or more important. Final considerations: If you have your projector at 3,5m or less, forget about technical screens. There might be exceptions, screens made specifically for your living room (I only know of one Japanese company doing that) but they are very, very expensive. If your projector is between 3,5m and 4m away from the screen, the distance is still short, and you will see some spot effect. However, depending on the conditions of your room, the great increase of contrast might be worth it. The wider the viewing angle of the screen, the less spot you will see, but the screen will be less immune to ambient light. 4m or more of distance between the projector and the screen is the ideal. Of course, personal taste is also a factor. The considerations above are what I recommend. You might have a different opinion, and as long as you’re happy with your setup, that’s good.
  5. On my part, I’m talking about the entire screen, naturally. It wouldn’t make any sense otherwise. With all the friendship I have for you, I ask you the patience to let me clarify something: I’m not fighting to sell screens here. Lusoscreen is a very small company and has a patent for glassless mirrors in Portugal (this means we have the exclusive legal right to produce and sell these mirrors in Portugal) that leaves us with difficulty to respond to all requests. Our screens exist today only because of my father’s passion for them. @Gregory Following the link you indicate, referring to our first flat screen, I can see in the photos that the screen has a correct orientation (either because it was measured on the floor, or because the projector was higher, or because of something else entirely). With this new screen the orientation was closer to the correct one when it was photographed on the floor.
  6. @dm27 If Mr. Gregory wants to go to the trouble of doing that, it would be interesting. I understand that making more holes in the wall might not be pleasant, though. Besides that, as far as I could understand from the posts in this forum, Mr. Gregory is satisfied with the setup he has in his home, and since there are 6 main elements that influence the end result of an image, maybe there is no need for him to be adjusting anything. On the other hand, I can personally guarantee that this screen (when correctly oriented) has a gain of approximately 0.9 (no less than 0.85 and no more than 0.95) and there is a relatively easy way for anyone that owns one of these screens to verify this. If you all allow me, Monday I can take a few pictures to demonstrate how to do that. If you think I'm over-stepping here I can send a PM.
  7. The correct orientation of the screen in that situation depends on the distance between the projector and the screen and how high they both are. Regardless of the size of the technical screen (any technical screen, not just ours), we recommend a minimum distance of 4 meters between projector and screen. But what if my room only has 3,5 meters from one wall to the other? There are solutions for this too. I know that there are projectors that have horizontal keystone correction in addition to the vertical one. If you don't know much about technical screens, it's easier to just place the projector in a way that the horizontal keystone is not needed (i.e. horizontally center the projector with the screen). But I can't place my projector in the middle of the screen, I can only place it 1 meter to the left. There are solutions for this too. When it comes to the vertical position of the projector, we should use the same logic we did for the horizontal position. But this is not always practical nor possible. So how do I orient the screen for @xano's situation? The easier way is to start with projecting a uniform color on the screen (most projectors show a blue color when they have no signal, this is good), then sit on the couch. Next compare the light on the top of the screen with the light on the bottom of the screen. If they don't have the same brightness, the screen needs to be tilted. When you find the position where the the light on the top of the screen and the light on the bottom of the screen are similar, you can lock the screen in that position. You don't need to be very precise, depending on the screen you are using there is usually not a precise angle, but more of a zone where things look okay. Many years ago screens would have a painted black border all around them. Lusoscreen started using velvet because it doesn't reflect light, and allows for better image cropping. Nowadays there are many manufacturers using the velvet too. More recently, but still about 20 years ago, Lusoscreen started supplying a wall support that allowed for the screens to be oriented. It's difficult to understand why some manufacturers of technical screens are taking so long to understand the benefits of it.
  8. I agree with you. That works well with cloth screens. Unfortunately with any technical screen (not only Lusoscreens) that way doesn't work. That's why we send the wall supports together with the screens. Those easily solve the problem of orienting the screens. I had already noticed that you hang the screens on the wall without the supports. I'm sorry for not saying anything because having projectors on the ceiling is no longer such an issue as with previous screens. The way that things were placed for your test, what happened was situation A above: the light of the projector hit the screen and was directed to the ceiling. The viewing angle is defined as the curved arrow with 2 ends. Tilting the screen, like in situation B, would yield better results, as the light of the projector would be directed towards the audience. Please note that this is true not only for all Lusoscreens but also for all other technical screens. Even cloths with positive gain (silver, pearled, nacré, etc) would improve from this tilting.
  9. I did not know about that website. Seems to have a problem with repeating thank you's but otherwise really good. Thanks.
  10. Mr. Zx10ryann36, Thank you very much for the translation. I tried translating with Google, but when I translated the result back, it had nothing to do with what I had written. I don't want to risk saying something inappropriate. Fortunately there are always nice people willing to help.
  11. Hi Mr. Gregory, It has been a while since I've been here. Can I know where you placed the projector to run the tests? On a table? Can you please tell me what is the height of that table and how high did you place the screen? I'm convinced that the screen has a gain of about 0.9 and the difference between this and the value you measured is very high. I'd like to try and understand what was the reason behind that value.
  12. Mr. Hervey, I just sent you a Personal Message with some tests I'd like you to do, so we can find out what is happening. Best regards, Paulo
  13. Hi everyone. Sorry for not being here more often and, once again, apologies for only speaking in English. I want to apologise to Mr. Yann if we mislead him. We sent him a foot support because he was going to demonstrate our screen with no time to prepare walls to hang the screen on. So it was the fastest way for him to show the screen and orient it correctly. However, the screens don't usually include a foot support. It would be an added cost that a large majority of people wouldn't use, so it would either be left gathering dust in a corner or it would go directly to the trash. The foot support we sent Mr. Yann was also made in a hurry and is not what you'd call pretty. In the future we will try to imagine a good structure to hold the screen that we can sell separately to people who want it. Now about the orientation, let me add a little more to what has been said. What I'm going to tell you now is true for ALL screens. Of course, matte white screens have such a high tolerance that it makes no sense to be worried about this, but all other screens, specially the technical screens can benefit if you take these tips into consideration: If the screen is very high and vertical, the light of the projector will pass above my head. If I tilt the screen down a little, I can direct the light to me. How do I know what is the best position? If I project a single-color image (like the blue that many projectors show when there is no signal) I must orient the screen until the top and the bottom of the image have exactly the same brightness when I'm sitting on the couch. Looking at the above picture, the projector is too high and the screen is vertical. The light is being directed at the ground. In this case there are two things that can be done: we lower the projector, we tilt the screen up, or we do both. The correct position is, once again, to check the brightness of the top and the bottom of the image while projecting a uniform color. One last case: here the screen is too low and the projector is too high. Just like before, there are many solutions here. Tilt the screen up, lower the projector, raise the screen or all of them. I hope this helps a little. It's never too much to repeat: don't put windows or other light sources behind the projector. I wish you all a nice day. Enjoy your movies.
  14. Hello coco, Sorry for taking so long to respond. With Christmas approaching, we received a large order from one of our representatives and we're a bit busy. The motorized screen is only waiting for better economic conditions on our part to begin production. We're still missing one of the molds so we can make the bottom bar (the one that is weighted to stretch the fabric down). We've been making motorized screens for a while (white cloth) but the bar on the bottom is too lightweight to be used with tensioned screens. In Portugal, the price for our motorized screens is frankly cheaper than the rigid screens, and I expect the tensioned screens to also be cheaper. For now, Mr. Yann is our representative. Assuming he'll continue to be when we lauch that screen, he'll be the one to make the price for France.
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