Buyers Guide

Introduction

3:2 Pull Down

3d Projection

Aspect Ratio

Brightness

AV Connections

Contrast Ratio

Lenses

Projector Lamps

Projection Panels

Resolution

Scan Signals

Screens

Wireless

Glossary

Installing a projector

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Installation can be as easy as positioning the projector on a table or bookcase and running a video cable to your laptop or DVD player. If you require your projector to be ceiling mounted you will need to run power and video cables. Although current projectors are designed for easy installation, Ceiling mounting and running power requires a licensed professional.

Positioning

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Most projectors give you four positioning options:

	Front - Simplest of all installations, only requires power connection and signal connection. Image size can be adjusted by simply repositioning the projector and altering the zoom lens (when available). This can also help in reducing the length of the video cable improving signal quality and eliminating the cost of expensive cabling.
	Ceiling - Fixed installation, requires image inversion, cabling for Video and power to ceiling and a ceiling mount. Before fixing you will need to calculate the required throw distance for your desired image size and the image offset (See Below). Please note that ceiling mounting in hot climates can reduce the effectiveness your projectors cooling system and may lead to lamp failure. Note: See your projector manual for instructions on inverting your image.
	Rear - Offers the same easy installation as front but requiring horizontal image inversion and a rear projection screen.
	Rear Ceiling - Requirements are the same as both Ceiling and rear.

If you need to position your projector to the left or right of the room or above or below the screen. Your image may suffer distortion of the image dimensions - Keystoning.

 

In this situation it is preferable to use Lens shift over Keystone correction. Keystone correction is also referred to as 3D-reform and Side-shot.

• Lens shift changes the projected image inside the lens maintaining the maximum resolution of your image.
• Keystone Correction squeezes the image displayed on the projection panel (lcd or dlp etc) to counter the projected image distortion, this reduces the number of pixels used on the panel and lowers the image resolution. For example "A" in the above image would be corrected by reducing the left hand side of the image on the projection panel.

Most projectors have vertical Keystone Correction to correct problems "C and D" above, only some come with Horizontal Keystone Correction which allows positioning of the projector to the left or right of the screen. Horizontal tends to have a lower angle if adjustment than vertical correction.

 

Screen size and Throw distance

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Screen Size, normally measured in inches is the diagonal distance "A" shown. The Throw Distance is the distance from the lens to the screen surface - "B" The ratio of  Throw distance over Screen size is the Throw Ratio. This ratio allows you to calculate the image size at any given distance or the throw distance for any given screen size.

 

Image Offset

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Image Offset - Quoted as a percentage, is the height of the image "H" divided by the height that the image is projected above the horizontal from the lens "C". This should be considered when calculating the position of your screen especially for ceiling mounting as it reduces the need to use extendable ceiling brackets to lower your projector. (note: projectors with Lens Shift do not have a quoted offset)