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A hardware device that enables an image, such as a computer screen, to be
projected onto a flat surface. All video projectors use a very bright light to
project the image, and most modern ones can correct any curves, blurriness, and
other inconsistencies through manual settings. Video projectors are widely used
for video conference, room presentations, classroom training, and home theatre
applications.
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Common display resolutions for a portable projector include SVGA (800×600
pixels), XGA (1024×768 pixels), 720p (1280×720 pixels), and 1080p
(1920×1080 pixels).
The cost of a device is not only determined by its resolution, but also by its
light output, acoustic noise output, contrast, and other characteristics. While
most modern projectors provide sufficient light for a small screen at night or
under controlled lighting such as in a basement with no windows, a projector
with a higher light output (measured in lumens, abbreviated “lm”)
is required for a larger screen or a room with a higher amount of ambient
light. A rating of 1000 to 1500 ANSI lumens or lower is suitable for smaller
screens with controlled lighting or low ambient light. Between 1500 and 3000 lm
is suitable for medium-sized screens with some ambient light or dimmed light.
Over 3000 lm is appropriate for very large screens in a large room with no
lighting control (for example, a conference room). Projected image size is
important; because the total amount of light does not change, as size
increases, brightness decreases. Image sizes are typically measured in linear
terms, diagonally, obscuring the fact that larger images require much more
light (proportional to the image area, not just the length of a side).
Increasing the diagonal measure of the image by 25 % reduces the image
brightness by 35 per cent; an increase of 41 per cent reduces brightness by
half.
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