Video Systems in AV
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Basic and Advanced Theory - Part 1
This is a start of a new module, where I will be focusing on Video Systems, and how this is used in the AV industry, starting with:
Origins of Projection Technology
Projection Evolution
Projection Screens
LCD, DLP, LED and Laser Projectors
Basics of Projection Mapping
Rental and Integrated LED Screens
Pixel Mapping and LED Controllers
Commercial LED screens/ Panels
Touch Screens
Video Cameras
Video Switchers
Broadcast Video Systems
Origins of Projection Technology
The first known origins of a “Movie” Projector, was first introduced in England in 1879 by a British Photographer. The device uses glass slides of film that rotate quickly to give the impression of a moving picture.
Moving forward to 1895, Woodville Latham and his sons, Otway and Gray, demonstrate their “Panopticon,” the first movie projector developed in the United States. Although motion pictures had been shown in the United States for several years using Thomas Edison’s Kinetoscope, the films could only be viewed one at a time in a peep-show box, not projected to a large audience.
Brothers Grey and Otway Latham, the founders of a company that produced and exhibited films of prize fights using the Kinetoscope, called on their father, Woodville, and W.K.L. Dickson, an assistant in the Edison Laboratory, to help them develop a device that would project life-sized images onto a screen in order to attract larger audiences.
Projection Evolution
Corporate America was first introduced to projection technology in the 1950s. Although the technology itself has changed dramatically since that time, conceptually it has remained the same. The opaque projectors which were the sole option of the 50’s have given way to a multitude of options in the 21st century where one’s choice of technology will likely hinge on the material to be projected.
Opaque Projectors - One of the earliest forms of projection, allows the user to project printed material or small objects without having to convert them to another medium. An example of such an application would be projecting the contents of a single page of a book onto a wall. This is achieved by turning to the page and placing the entire book into the opaque projector.
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| Braun Paxiscope-XL Opaque Projector |
Slide Projectors - These have also been around since the 1950's, and unlike opaque projectors, slide projectors require that the presented material be transferred to a 35mm slide allowing the user to project virtually anything that can be put on film. With the use of different lenses, images could be projected onto larger surfaces from further distances away.
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| Elmo Omnigraphic 301 Carousel Cartridge 35mm Slide Projector |
Overhead Projectors (OHP’s) - In some ways an overhead projector is another form of still image projection, but in this case a transparent sheet of flexible material known as a transparency is used to write directly onto with a marker. In some cases, images could be directly printed onto the transparency sheet. OHP’s were introduced into U.S. military training during World War II as early as the 1940’s and were quickly being taken up by tertiary educators, and by the 1950’s, they were being used in corporations.
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| Overhead Projector |
CRT Projectors - CRT projectors are video projectors that use a small, high-brightness cathode ray tube (CRT) as the image generating element. The image is then focused and enlarged onto a screen using a lens kept in front of the CRT face. The first color CRT projectors came out in the early 1950s. Most modern CRT projectors are color and have three separate CRTs (instead of a single, color CRT), and their own lenses to achieve color images.The red, green and blue portions of the incoming video signal are processed and sent to separate Red, Green and Blue CRT’s, whose images are focused by their lenses to achieve the overall picture on the screen.
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| Sony CRT Video Projector |
Computer Projectors - the fully integrated digital data projector came into existence in the early 1990's and served primarily as a computer display projector for business, education and training. Earlier forms of LCD (Liquid Crystal Display) projectors were very low in brightness, and produced as low as 220 ANSI Lumens from a 575W Metal Halide bulb. An OHP at the time could produce as much as 3,000 ANSI Lumens of brightness or more, so the earlier LCD Projectors did not possess sufficient brightness for larger audiences.
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| Liesegang 575 LCD Projector |
Projection Screens
A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Uniformly white or gray screens are used almost exclusively to avoid any discolouration to the image, while the most desired brightness of the screen depends on a number of variables, such as the ambient light level and the luminous power of the image source.
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| Movie Theatre Screen |
Types of Screens in different settings
Commercial Movie Theatre - In commercial movie theaters, the screen is a reflective surface that may be either aluminised (for high contrast in moderate ambient light) or a white surface with small glass beads (for high brilliance under dark conditions). The screen also has hundreds of small, evenly spaced holes to allow air to and from the speakers and subwoofer, which often are installed directly behind it.
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| Example of a commercial theater screen front projection fabric |
Fixed-frame screens - These screens provide the greatest level of uniform tension on the screens surface, resulting in the optimal image quality. They are often used in home theater and professional environments where the screen does not need to be recessed into the case.
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| Example of a fixed-frame Home Theater Screen |
Pull-down and Electric screens - Also known as manual wall screens, are often used in spaces where a permanently installed screen would require too much space, such as a classroom or lecture hall. These commonly use painted fabric that is rolled in the screen case when not used, making them less obtrusive when the screen is not in use.
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| Manual Pull-down Screen |
Electric screens are similar to pull-down screens, but instead of the screen being pulled down manually, an electric motor raises and lowers the screen, using either a remote control or wall-mounted switch. Electric screens can be wall-mounted, ceiling-mounted or ceiling recessed. These are often larger screens.
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| Electric roll down screen example in a home theater setting |
Mobile screens - These screens usually use either a pull-down screen on a free stand, or pull up from a weighted base. These can be used when it is impossible or impractical to mount the screen to a wall or a ceiling. These screens were typically used for Overhead Projectors as well as Slide Projectors, but can also be used with LCD Projectors.
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| Tripod Mobile Pull-Up Screen |
Fast-Fold Screens - This is another form of portable screen, but makes use of a rigid frame, which is then mounted onto legs that is attached on either side of the frame, so that the screen is freestanding. Fast-Fold screens are usually larger in overall size, and are mainly used within larger venues where there’s a need to display video or still content.
The frames and legs are typically made from Aluminium, which makes setting up lightweight and simple. The frames and legs are designed to fold up and then be packed into a portable case for transportation. Fast-Fold screens can be purchased with front and rear projection fabrics, as well as dress kits, which attach to the frame to give the screen a theater appearance.
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| Fast-fold front projection screen |
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| Fast-fold front projection screen with black velour dress kit |
Inflatable Screens - These are large format screens, that are mainly used for outdoor movies, film festivals, drive-in theaters, sports, social, fundraising and other events requiring outdoor projection. They make use of an inflatable framework attached to a projection screen, and the inflatable framework is usually tethered for safety purposes.
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| Inflatable screen open air cinema |
Front, Rear and Twin Projection screen surfaces
Front and rear projection screen surfaces refer to the orientation of the projection method that is used in accordance with a specific setup or room orientation.
Front Projection screen surfaces are designed for use with a projector that is placed in front of the surface, which then projects onto the screen. This also means that the projector is on the same side as the audience viewing the screen. Front projection surfaces are usually matt white, which diffuses projected light in all directions, so the projected image can be seen from any angle.
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| Snap on Fast-Fold front projection screen surface |
Rear Projection screen surfaces are designed for use with a projector that is placed behind the screen surface. This means that the audience is at the front of the screen, and the projector is placed behind the screen. A rear projection screen surface functions as a diffuser and generally has better contrast. The material is usually translucent gray and allows light to pass through from the rear of the screen surface, to be viewed by the audience viewing the screen from the front.
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| Snap on Fast-Fold Rear Projection screen surface |
Twin projection screen surfaces are also available as well, meaning that the screen surface can be used as either a front or rear projection screen, or even for simultaneous front and rear projection.
The screen material is a combination of front and rear projection screen material and specifically designed to accommodate both projection methods.
Quick Recap
So far we’ve learned the following:
Video projection can trace its origins back to the late 1800’s
Projection technology have evolved immensely since the 1950’s
There’s many Projection screen options available to cater for most applications
It’s best to always consider your venue orientation before deciding on what projection method and screen type you would require.
Next Up…
We go through the differences between LCD, DLP, LED and Laser Projectors
The basics of Projection Mapping
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