Screen Goo is a line of specially formatted acrylic paint products designed specifically for video projection applications. It allows anyone to transform a wide variety of paintable substrates into high performance front, rear and 3D projection screens.
Roll On Projection Screens
Kevin Nute | Goo Systems
Roll On Projection Screens
Author: Kevin Nute, Goo Systems
Screen Goo is a line of specially formatted acrylic paint products designed specifically for video projection applications. It allows anyone to transform a wide variety of paintable substrates into high performance front, rear and 3D projection screens. Screen Goo paint products are ideal for Home Theater, Commercial, Entertainment, Educational and Industrial applications.and can be used both indoors and outdoors. Screen Goo is inexpensive. It costs a fraction of other far more expensive yet lower performance alternatives, it can be painted into any size/shape screen and most applications can be done by users without any special tools or skills
With flat panel HDTVs continuing to decrease in price, why would anyone buy a projection system for home/commercial use?
So, 60” flat panel televisions can be had for well under $3,000.00 these days; why would anyone buy a projector?
The first reason is simple: size matters! A 60”, 16:9 display represents about 11 square feet of picture size whereas even a relatively small projected image at 92” diagonal is about 25 sq. ft. or, if you prefer, better than twice as much picture!
So why is size important? In a home environment, these larger video displays are used primarily for entertainment. Whether we're watching movies, sporting events, concerts or playing video games, we're looking for something to take us out of the everyday (???) and into another, for a lack of a better word, space.
The more believable our sense of being immersed in this “space” is, the more engaging the whole experience becomes. The corollary to this with respect to image size is that the more the picture fills our field of vision the more we feel like we're part of the action. One of the keys to achieving this sensation is to make sure that the image is wide enough so that we have to move our eyes to focus on the far edges of the picture. This changes how our brain processes visual information; you could say that it forces us to actively watch as opposed to simply seeing. Our eyes are particularly sensitive to motion on the peripheries of our vision and any activity in those areas really gets the old adrenaline going while we decide if fight or flight is the appropriate response to what we've just seen out of the corner of our eye! You would have to sit awfully close to 60” display to trigger this sense of immersion and it would only be available to one, maybe two viewers at a time.
In a commercial settings the benefits of image size are simpler to understand: it's possible to catch and convey your content to way more eyeballs for the same investment if your image is 50 sq. ft. (130” diagonal) or larger as opposed to 10-11 sq. ft.
What is the role of the screen in a projection-based video system?
In simplest terms a screen should provide the most suitable reflective surface for the light and content produced by a projector. This is straightforward enough until we start to look a bit more deeply at what is meant by suitable. Going back to the earliest days of motion pictures (way before video!) the job of a screen was, in some ways, more difficult but, at the same time, far more predictable. Early film projectors produced relatively small quantities of light meaning that movies could only be projected in very dark auditoriums and screens had to return a very high percentage of the light produced by the projectors. The good news is that these limitations meant that early screen makers knew rather precisely the circumstances their screens were going to be used in. To simplify matters even further, colour wasn't an issue; all of the content was black and white or, more correctly, monochrome. Finally, there were only a handful of projector manufacturers producing a very narrow selection of models. Therefore, while the job of a screen was difficult, it was largely predictable and one type of screen worked well in virtually all types of applications.
Well, things have changed! There are dozens of projector brands representing hundreds of models. Projection is used in a huge variety of applications representing different circumstances and settings and almost every conceivable level of ambient light. But this hasn't changed the role of the projection screen; it still needs to reflect the content accurately and in a manner that allows for contrast appropriate to the circumstances it finds itself used in.
Why aren’t all screens white?
The short answer is because all projectors aren’t used in rooms with complete light control.
Let’s consider two crucial but largely misunderstood aspects of video projection.
The first is what is meant when we say “black”. In casual conversation, and in many fashion circles, black is often referred to as a colour. Technically, this is incorrect: black is more properly defined as the absence of light and colour. In video terms black is literally nothing.
If we look at the input signal of a video in electrical terms, what we see in the areas of the signal representing black in the image is: nothing! And this is what the projector is being asked to produce when the image calls for black: nothing; no light and no colour.
This is brings us to our second common misperception: that projectors “produce” black. We’ve all seen projector reviews and promotional literature where a projector is referred to as producing “excellent black”. As we’ve seen with our definition of black, this claim, strictly speaking, just isn’t accurate. All a projector can really do is maintain black; it can’t produce it.
Projectors have been getting better at controlling stray light (the “something” in a projector which compromises the “nothing” that black is meant to be) which has improved their measured contrast ratio specifications and their image quality. Yet using a projector with a stratospheric contrast ratio spec does not mean that the user can expect to see believable black level reproduction in all circumstances. Irrespective of whether a manufacturer claims a contrast ratio of 1000:1 or 100,000:1, and recalling that black is the absence of light, any light falling on the screen compromises the maintenance of true black.
Consider this: imagine yourself in a reasonably well lit room. You are looking at a white projection screen. It appears white, to you the observer, because it is reflecting the white components of the light in the room.
Stick with me here for a brief digression: if you were to gradually lower the levels of light in the room to complete darkness, the observer’s perception of the white screen’s colour would move through progressively darker shades of grey until, when the room reached complete darkness, the screen becomes invisible or “black”. Fire up a projector under these circumstances, absorb the light from the projector being reflected from the screen with dark, non-reflective walls and ceiling and you can expect to perceive a reasonable sense of black in the projected image. However, bring the lights back up with the projector off. The screen starts to look white again.
Well, given that we’ve established that projectors can’t produce black, it’s reasonable to assume that they also can’t “throw” black across the room. What this means is that the perceived lightness or darkness of the screen is in fact the actual black level of the projected image. There is no possible way for the projector to “throw” black across a room and “darken” a white screen. So what to do if you want a reasonable approximation of black, and therefore, decent contrast, in a projected image in a room with ambient light?
Look to the screen for help!
A grey screen starts off darker than a white screen and, assuming it is colour correct (more on this in the next section), is, in terms of maintaining black, functionally the same as dimming the lights. So the answer to the question: “why aren’t all screens white” is: “because not all rooms are fully dark”.
How is Goo the same as a conventional screen?
A conventional screen can be described as a piece of material which reflects light in a manner which its manufacturer considers conducive to the accurate reproduction of a projected image. Some screens from reputable manufacturers do an excellent job of this while others are surprisingly poor at it. Much like a boomerang that doesn’t come back could be referred to as a stick, so a screen that does not accurately reflect projected light could be called a shower curtain or a boat cover Other than to say caveat emptor, we’re going to ignore these inferior screens and discuss how Screen Goo compares to “proper” projection screens. In order to do that, we need to define what constitutes a proper reproduction of a projected image. Let’s look at three main areas:
- Color accuracy
- Image geometry
- Image uniformity
Let’s start with colour accuracy. While the presence of Tint controls on colour televisions since their introduction has given many viewers the impression that “good” colour is a matter of taste, we can actually be much more scientific in our definition of what constitutes correct colour.
A good beginning, perhaps a bit counter intuitively in a discussion of colour, is to look at white. OK, so which white? White walls in a newly constructed house? White paper? White clouds? A white dress shirt? As the preceding examples indicate, what we call white can mean many different things. So how can we quantify these differences and how can we arrive at a “correct” white?
In numeric terms, we can express and measure different whites using a scale based on something called colour temperature. Many of you will be familiar with the idea of a warm white, which tends toward red and orange like sunlight or a cool white, which tends more towards blue like a lot fluorescent lighting. These examples correspond pretty well to measured colour temperatures and are sufficient definition for the purposes of this discussion. Those of you who want to take a closer look at this topic can do so here:
All we need to know at this point is that there is a correct colour temperature for video; that it was settled on back in the prehistory of colour television broadcasting and that it is still in force today. Specifically we’re talking about a colour temperature of 6500 degrees Kelvin. In terms of “warm” and “cool” it falls, of course, somewhere in the middle and is often defined as the quality of light one could expect to see at noon on an overcast day.
If that seems a little vague, well it is, which is why we’re going to look at another way of defining the reference white colour temperature and doing so with a very high degree of precision. To do that we need to talk a bit about how colour works in video terms. All colours in video are recorded and reproduced using just three primary colours: Red, Green and Blue or RGB. Each of the billions of colours reproducible by current video projectors, including our reference white, can be expressed as a specific ratio of red, green and blue. We can also measure colours in terms of their ratios of red, green and blue.
Here’s the beauty of a reference white: when it is correct so are the rest of the colours.
How does this relate to Screen Goo and how it compares to “regular” screens? Screen Goo surfaces all measure to 6500 degrees, meaning that they are colour accurate. This, perhaps somewhat surprisingly, is only true of select few premium regular screens.
How about image geometry? Here Screen Goo enjoys a clear advantage over virtually all regular screens. Vinyls stretch, sag and curl. Even very expensive, tensioned screens are rarely truly flat.
Why is this important? Because the flatness of the viewing surface will a have clear impact on the accuracy of the geometry of the projected image. Wrinkles and sags in the viewing surface will distort the geometry of the projected image. This geometric distortion can be subtle or blatantly obvious but in all cases it will impart a sense of unease in viewers and contribute to viewing fatigue. Provided Screen Goo is applied to a flat surface, and the projector is properly set up, its geometric accuracy will be superior to that of conventional vinyl screens. This plays a significant role in the sense of “rightness” and ease viewers experience when watching a Goo screen.
Image uniformity describes how evenly different areas of a given screen reflect light from a projector. A screen that reflects the same amount of light from the corners as it does from the centre is said to display a high degree of image uniformity. A screen that reflects noticeably more light from the centre
is said to hotspot. Goo Screens, due largely to the highly diffusive nature of its semi translucent finish coats, are as uniform as any screen available.
So how do Goo screens differ from regular screens?
An important difference is flexibility. A Goo screen can be any shape or size with no seams. Screen Goo can also be used to coat an entire wall rather than simply creating a defined shape or size. There any many advantages to this approach. First, it’s visually very stealthy: when the projector is turned off, the screen “disappears”. This approach also eliminates the need for expensive masking strategies when displaying a variety of aspect ratios. On a Goo “wall” the projected image will appear to “float”; the absence of a defined border means that, irrespective of image size or aspect ratio, the viewer will never be left with the sense that something is missing. Nor will a viewer be tempted to stretch or otherwise distort the image in order to “fill” a defined space.
So what about price?
Conventional screens are available at a wide variety of price points. Some are very inexpensive; unfortunately they are more expensive than the shower curtains and bedsheets whose performance as projection screens they most closely mimic Quality projection screens, meaning screens that are colour accurate and display a high degree of uniformity tend be on the pricy side. As an example, a well known California based screen manufacturer, which bases a lot of its marketing on the Academy Award in its trophy case, makes a white surface which is widely recognized and justifiably praised as an excellent projection surface. A Screen Goo Reference White surface is every bit as colour accurate as the California surface, has a higher degree of image uniformity and costs on average less than 10% than the price for a comparable sized screen.
Why not just use regular paint?
Wall paint is designed and engineered principally to cover an underlying surface and to provide color in a room. These are relatively straightforward objectives and they are accomplished by house paint manufacturers through the use of an inexpensive dispersion medium (typically, water-based acrylic or an oil-based medium) to which a pigment or pigments are added to provide color. Usually, relatively small amounts of pigment are used and then supplemented with extenders whose main purpose is to reduce the amount of expensive pigment required to produce the desired color. This can be done because the quantity of light reflected by wall paint is relatively unimportant.
By contrast, Screen Goo has been specifically engineered to accurately reflect and disperse the complex coloured light patterns produced by video projectors. To that end, Screen Goo starts by employing a premium acrylic dispersion with very low light absorption characteristics and excellent durability. To minimize light loss and to ensure colour fidelity, Screen Goo uses much greater concentrations of pigment than those found in house paint. These pigments are carefully chosen to accurately reflect the full spectrum of colour produced by video projectors as opposed to house paints where the goal is to reflect that portion of the light which produces the single desired color. In addition, Goo Systems employs proprietary dispersion and pigment treatment techniques to maximize the reflective properties of the pigments employed. These techniques require custom built machinery and are very time and labour intensive.
Lastly, unlike wall paint which involves the application of a single product, a Screen Goo application consists of two very different coatings. Screen Goo Reflective Coats provide an ideal reflective surface to which a diffusive, semi-translucent colour correct Finish Coat is added. It is the combination of the reflective Reflective Coat and the diffusive Finish Coat which gives a Screen Goo screen its remarkable qualities of high reflectivity, colour accuracy, wide viewing angles and excellent contrast. The icing on the cake is the very special sense of image depth, or feeling of looking into the picture that only a Screen Goo screen provides.
Do I need a specially prepared surface?
The surface to which Screen Goo is applied will affect its performance; the flatter and smoother the surface, the better the finished result. If you’re going to be applying Goo coatings to new drywall construction, let your contractor know that you want a level 5 drywall finish for your Goo wall.
How often do I need recoat?
If you use your Goo screen in a smoke-free environment and away from the predations of children. pets, or rambunctious sports fans, your Goo screen will last indefinitely!
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