SANYO

Conventional television systems use a scanning method that displays two low quality interlaced 'fields', which when combined form a single higher quality 'frame'. Each frame is displayed 25 times every second, but the fields/frames are shown so rapidly that the eye perceives a high quality moving image, and not a series of low resolution still images. A projector or DVD player that uses progressive scan reconstructs the image using complete frames, and the result is a more natural, stable picture, with fewer effects like flicker and picture shimmer that interlacing can introduce.

The amount of detail that is visible in an image displayed on your computer screen is expressed in terms of the number of distinct horizontal and vertical lines that can be resolved. The maximum number of lines that can be seen when a standard test pattern is displayed is called the resolution. Computers have set resolutions, commonly called VGA, SVGA, XGA, SXGA and UXGA.

When a projector is projecting an image at a screen that is directly in front of and at right angles to the axis of the lens, the sides and the top and bottom of the image will be straight and parallel. If the projector is then tilted upwards, the image will change shape, with the top of the picture becoming wider than the bottom. If the projector is tilted downwards, the reverse will happen and the bottom of the picture will become wider than the top. This is called 'keystone' error or distortion. If your projector is equipped with keystone correction, it can electronically correct this distortion by digitally resizing the image until it becomes rectangular again, with parallel sides. Although this feature can be very useful at times, its use should be avoided when possible, because a certain amount of picture degradation always results due to the rescaling involved in the process.

Optical lens shift physically moves the projector's lens assembly vertically or horizontally in relation to the LCD prism, without introducing any keystone distortion. Projectors which incorporate this feature are more versatile allowing for a more flexible set up, because the positioning of the projector relative to the screen is less critical.

An S-Video (separate video) signal in one in which the luminance (brightness) and colour (chrominance) information relating to a particular image are separated and carried as individual signals. Wherever possible, s-video signals should be used in preference to composite signals, which because all the individual parts are mixed together and can interact, often introduce noise and effects such as colour 'bleeding'.

A composite signal is one that contains all the information relating to a particular image. The luminance (brightness) information, colour information, blanking and synchronizing signals are all mixed together to form a combined or composite signal.

The panels in an LCD projector have a fixed resolution and produce the best results when fed with a signal that has the same number of vertical and horizontal lines. i.e. a projector with LCD panels having 1280 x 1024 pixels is said to have an SXGA native resolution, and will produce best results when fed with a signal having 1280 lines x 1024 lines. The image quality benefits in matching the resolution of the projector to the source computer are considerable, as the projected image will then match the computer image pixel for pixel, giving the best possible reproduction. If the source has more lines than the projector then some are lost, losing picture information, and if the source has too few lines the picture does not make full use of the projector's resolution. Sanyo projectors, however, utilize advanced technology that automatically detects and resizes pictures seamlessly regardless of their native resolution.

VGA is an acronym for Video Graphics Array, and all these terms are a measure of the resolution of the signal being generated by a computer. A VGA signal has a resolution of 640 vertical lines x 480 horizontal lines; SVGA is 800 vertical lines x 600 horizontal lines; XGA is 1024 lines x 768 lines; SXGA is 1280 lines x 1024 lines and UXGA is 1600 lines x 1200 lines. A resolution of 1024 x 768 (XGA) tends to be the most common standard output in laptop computers and, therefore, the most popular resolution for projectors as well.

Contrast is the difference betwen the brightest and the darkest areas of an image, and helps to define the depth of the information comprising the image. High contrast is useful when showing high quality video in limited ambient light, but is not as necessary if displaying simple computer images such as spreadsheets. The contrast ratio is a measure of the brightness limits of an image, brightest to darkest, and a good projector will have a contrast ratio of something like 300:1 or better.

In general, the brighter the image a projector can produce, the more impact a presentation will have on its audience. As a rough guide, 500 ANSI lumens per square metre of screen under normal office lighting, will give a bright and well-contrasted image. So something like 1000 ANSI lumens will be quite satisfactory for a small group of people in an office. Higher light output allows for presentations of larger images to bigger audiences, but ambient light and the quality of the screen as well as its size can dramatically affect image brightness. A working demonstration by your dealer is the best way to evaluate the product.