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How Much for a projector?

Technology - by - June 24, 2008 - 04:39 Etc/GMT+5 - Be first to Comment!

With the failure of the primary video projector during service this week, now is a good time to re-examine the practical aspects of how to choose a projector.

Why do we need such an expense as a projector?
When choosing an appropriate projection system one must consider the needs to be met and choose the components to satisfy those requirements. Light, room and screen size, and resolution are the variables to be considered.

The lighting conditions in the space will determine how bright the projection image must be to be seen clearly and with proper colors and definition. Just as the light from the projector reflects off the screen so one can see an image, the light in the room also is reflecting off the screen (usually WHITE light), competing in brightness with the image. Add to this a fundamental problem with projection – with dark areas of the video or image, you are trying to make a WHITE screen surface appear BLACK! Luckily, eyes have a limited range of sense from the brightest area of an image to the darkest area, so all we have to do is make what is suppose to be white or bright much brighter than the areas that are suppose to be dark or black. How bright of a projector that is required to do this depends on how much room light is reflecting off the screen causing the darker areas to be light. A movie theater is relatively dark, so it doesn’t take a real powerful projector to make the bright areas much brighter than the dark areas. A sanctuary and platform with lots of bright lights, however, requires a bright powerful projector to produce an image.

The size of the screen also determines how big a projector is needed. A finite amount of light comes out of the lens of the projector (measured in Lumens) and begins to spread. The farther the screen from the projector, the more the light has spread out and the larger the image. The problem is that finite amount of light is spread out over a larger and larger surface area, thus the amount of light reflecting back from any one area of the image is less and less. This is why a larger screen requires a more powerful projector than a small screen.

The viewing environment and use of the screen determines the size of the screen. A screen for a movie needs to be big enough to envelop the audience, to transport them into the movie and help them forget they are sitting in a theater with a couple hundred other people. A screen for a presentation needs to be large enough that the people sitting farthest from the screen can see and understand the images being shown. A screen for displaying lyrics and scriptures needs to be large enough that six to eight lines of text easily fit and can be read from the back of the room. Studies have shown that the optimal height of the screen should be 1/6th to 1/8th the distance to the last row of seats. For a sanctuary where the last row of seats is 120 feet away, this translates to a screen that is 15 to 20 feet tall. But don’t forget the front row, if the screen is too big they will not be able to view the entire screen from edge to edge, so the distance to the back row should be balanced with the distance to the front row, or more than one screen should be used, each covering different viewing areas. The width of the first row also effects the screen size and placement choices. As with many other things technical, tradeoffs need to be balanced in choosing the screen size.

How close the congregation is to the screen determines the need for resolution of the image. The closer people are to the screen, the more likely they will be able to see the individual pixels that make up the image. The larger the projected image is, the larger these pixel blocks are. Seeing individual pixels causes images and text to look jagged and grainy. With projection and other digital images there is also the “screen door” effect, where the black lines between individual pixels break up the image. When combined with motion video, this causes annoying artifacts for some, while other people are so sensitive to it as to feel motion sick – not the best atmosphere for worship. Those who study such things and set standards have determined the required resolution versus seating distances, based upon the human eye’s ability to discern the height of an image at a given distance. These standards can be applied to select the required resolution for the projection system.

Why won’t a consumer, portable projector work?
There are advertisements from the popular computer manufacturer or office supply house for inexpensive projectors that seem very bright. It is tempting to think that a thousand dollar projector will serve the congregation instead of spending tens of thousand dollars on a large venue projector, but that is seldom a satisfactory solution. There are some big differences between the consumer grade projector and the venue grade projector.

Large venue projectors can accept a wide range of lenses, so the proper lens can be chosen based upon the screen size and the best location to mount the projector. Portable projectors have a built in lens, which has a limited zoom range, limiting the distance from the screen these can be mounted. Because these projectors are often designed to be set up in conference rooms and class rooms front and center, the zoom range of the lens is designed to set the projector close to the screen – often impractical in a church sanctuary that holds more than 200 people (the typical size of a conference or class room).

Larger projectors are often designed for quiet and continuous operation, while portable projectors of often designed to be small and light weight. The consumer, portable projector uses noisy cooling fans to move a lot of air to keep them cool enough for short term use, but may overheat easier during long periods of operation.

Large venue projectors start at 4000 – 5000 lumens and are available up to 30,000 lumens plus, where as portable projectors typically are only available up to 3000 – 5000 lumens of brightness. As we have seen above, sanctuaries and worship centers often require much brighter projectors than a home theater or conference room, with the typical large screen requiring 10,000 to 12,000 lumens, much brighter than most portable projectors can provide.

There are many other specifications and room design factors that can help determine the right projector for the job, beyond the scope of this article, but the intent here is to give an overview of projection and the practical aspects of implementing it in a house of worship. For more information about projection systems, contact a church media consultant such as myself (jeff@essentricaudio.com) or let me suggest a design build firm such as Stark Raving Solution and let us design the right projection system.

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