A projection screen is probably the least considered factor in setting up a projection system. Do you need a screen at all?
What is the purpose of a projection screen?
The purpose of a projection screen is to reproduce visual information without losing image quality and to distribute the projected light towards the audience; it plays an integral part in the quality of the displayed image. Projecting without a screen will compromise the image in one or more ways.
How do projection screens work?
Projection screens maximize the light coming from the projector by reflecting more light back to the audience. They are made using high-tech fabrics, that either focus or diffuse the light shining on them and control how that light is reflected back to the viewer. With the lower light output of older projectors (below 500 Lumens), screens were a necessity to maximize the light and were generally "High Gain" . Now with the high lumen projectors (anything above 2000 Lumens) this isn't so important to have a high gain screen.
A projection screen has to reflect and distribute the projected image in such a way that everyone in the room can see and read the image clearly, so optimum image quality can only be achieved if the projector and projection screen are perfectly matched to the room.
A good option
in certain instances if to paint a wall. A painted screen can be cost effective,
long lasting and less intrusive. Obviously the right paint has to be used.
Projecting on an ordinary painted wall can scatter the light in the same way as
the beaded screens. Standard white paint is never white! the slight yellow colour will move the colour spectrum of the
projected image and can suffer from hot
spotting while the overall image brightness can drop (see below) . Specially
formulated paint is designed to stop spectrum colour creep, reduce hot spotting
and increase the contrast. After testing over 5 different paints, we chose the best
performing screen paint on the market -
Scream (Screen Cream)
paint products. In testing Scream was found to be as good as leading screens, great for inconspicuous screens inside and outside,
simply paint the hole wall white. It also has the flexability to be painted onto curved surfaces and glass for rear projection
Screens can alter light in 4 different ways:
1. Diffusive –
reflects with almost
2. Reflective –
reflects in the opposite direction to the source (if the
projector is ceiling mounted, light is reflected from
the screen back toward to floor.
3. Retro Reflective –
reflects back to the source
4. Rear Projection -
Light is difused through the screen
Screens can alter light in 4 different ways:
1. Diffusive – reflects with almost complete diffusion
2. Reflective – reflects in the opposite direction to the source (if the projector is ceiling mounted, light is reflected from the screen back toward to floor.
3. Retro Reflective – reflects back to the source
4. Rear Projection - Light is difused through the screen
A low gain screen is Diffusive and the material has a gain of between 0.9 and
1.3. i.e. it reflects 90% to 130% more light than the standard white magnesium
oxide board in exactly the same conditions.
High gain screens
A high gain screens are either Reflective or Retro Reflective and the material might have a gain of 1.8 or even 2.2. i.e. it reflects 180% or even 220% more light than the standard white magnesium oxide board.
With a high gain screen that is reflective a ceiling mounted projector will
reflect the light back at the floor, not necessarily where your audience is
So as you can see both Reflective and Retro Reflective offer a reduced viewing angle!
Generally when choosing the aspect ratio of your screen its worth taking into account the aspect ratio of your projector. If your projector is natively 4:3 match this with a 4:3 screen. This will give you the best effect filling all available screen space and optimizing the projected image.
Please remember: As a guide you should be at a distance from your screen less than 1.5 to 2 times its diagonal for that real cinema feel.
Housed inside the large cabinet of a rear projection unit is a projector aimed at a mirror that reflects the image onto the rear of a display screen.
The mirror enables the image to travel far enough to be seen without requiring the distance that front projection normally requires.
The mirror in a rear projection unit allows for large images while maintaining a relatively slim profile for the home or in the boardroom. A permanent rear-projection system can be installed into a wall for a neater and more impressive finish.
Rear projection screens also
have the benefit that people are less likely to walk between the
projector and the screen, casting shadows over the image.
Screen Size relative to Format
Consider this for a moment. Most people will install the widest possible
screen they can fit into the space available, regardless of its format.
Screen width is almost always the limiting factor. For example, in my
theatre space I had two choices. I could install a 16:9 screen that was
8 feet wide, or a 4:3 screen that was 8 feet wide. If I installed a 16:9
screen it would be 8 feet wide and 4.5 feet high. But if I installed a
4:3 screen, it would be 8 feet wide and 6 feet high. The 8-foot width is
limited by the room; the screen height is my option.
Front projection screens have been offered in a variety of different materials from glass beaded, pearlescent to grey and silver or silver-lenticular. All of these have been shown to have their limitations. The main reason for their use was their high gain or higher contrast over Matte white screen material but the gains come at a cost. But Matt white is by far the best overall solution for modern LCD and DLP Projectors.
- There has been a lot of marketing hype about grey front projection
screen materials which improve image contrast. Unfortunately, with
front projection, this results in a colour shift to the blue spectrum -
not a problem with black and white projectors but can create ghastly
problems with colour. For example, skin tones have a green, sickly
tinge. Your whites will also be slightly off-white. So why do they
sell, because when there is any ambient or reflected light in the room,
it will absorb the
and have an impact on perceived contrast more so than the contrast
capability of the projector.
Glass beaded screens have a higher gain however being retro reflective you will experience a dramatic loss of viewing angle and a loss of resolution. They are also mechanically unstable in that the beads can move or fall off entirely, creating very distinctive dark spots.
Pearlescent screens have a higher gain, however colour shift to red occurs and there is a tendency to hot spot. They also have a narrow viewing angle, are not readily available and are expensive due to high manufacturing costs
Silver/Silver lenticular screens also provide a higher gain, however these screens will cause a colour shift to blue, have a smaller viewing angle and can hot spot. These screens are great for old black and white, low power projectors but not suitable for contemporary projectors. However, this material is still the best medium for 3D projection
For the most flexible screen how about paint? If you don't like having to pull your screen up and down every time you want to watch a movie, or don't like the bands you get top and bottom when you watch a widescreen movie on a 4:3 screen (or left and right , watching a 4:3 movie on a 16:9 screen). Then how about painting the whole wall?
Scream (Screen Cream) paint has the capacity to outperform most of the existing screen products in use today. The paint is made from the highest grade acrylic available. By far the most popular for home cinema is the White as it easily blends in with most decor, In more commercial spaces from Churches to Bars and clubs the Light grey is popular to boost contrast ratio. Image quality is very high and can be better than a screen (depending on surface and the ability of the painter). There is also a rear projection paint that can be applied to glass, eg a shop window. For paint it's quite expensive but still cheaper than most large screens.
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