Whether it's to enjoy a full cinematic, surround-sound, audio-visual experience at home or to deliver a PowerPoint presentation at the office or classroom, modern projection systems can be expected to deliver excellent results. It's not surprising that they have become a 'must have' addition to many home entertainment systems as well as office and classroom audio-visual set-ups.
About Projection Systems
Projectors for home cinema, educational or business use come in a wide variety of sizes, styles, specifications and features. Various technologies are in use, the most common being LCD (liquid crystal display) and DLP (digital light processing). Other 'offshoot' technologies are also used by various manufacturers.
Projectors for Home Cinema Use
Both video and sound quality are the most important features of a home cinema or theatre projection system. A typical home cinema projector will be installed in a designated room and in a fixed location at the optimum distance from the screen. The projector may be placed on a suitable table or other conveniently located surface or may be permanently mounted overhead. Correct initial setup is critical in order to achieve the best possible cinematic entertainment experience.
About Office and Classroom Projection Systems
Projectors designed for classroom, office or other workplace environments have different demands placed upon them. They need to be more portable as they will most likely be used in a variety of locations. Set-up isn't absolutely critical as the projector won't normally be left in place but will soon be moved to another location as required. A quick and simple set-up procedure is important for school and work environments. Sound quality isn't nearly so important either. In many cases, sound won't even be required as the most common objective is to present visual information clearly - usually to the accompaniment of a live spoken commentary provided by whoever is delivering the video presentation. Portability and image sharpness are the most important considerations for projectors designed for classroom and office use.
Projection System Features
While manufacturers may employ different technologies to build their projectors, users are more interested in what projectors deliver than in how they achieve it. Image quality, sound quality, reliability, portability, and price are far more important considerations for most people considering the purchase of any projection system.
A projector's brightness is measured in lumens as stated in its specifications. In darkened rooms, depending on other factors such as room size, viewing distance, and screen reflectivity, a projected image can be too bright for comfort. Increasing the ambient lighting a little can help as it reduces the 'apparent' brightness. In office or classroom use, daylight or other ambient lighting is usually present anyway. Ambient light also tends to reduce the projected image contrast, but the effect is less noticeable with projectors that have greater brightness. When comparing projector specifications, make sure to compare the brightness levels stated in lumens.
Contrast range refers to the difference in brightness between the brightest and darkest image levels that the unit is capable of projecting. A ratio given as, for example, 4,000:1 means that the brightest tone that a projector can produce will be four thousand times brighter than its darkest tone. Good contrast range makes for a more pleasing viewing experience. Manufacturers usually specify the contrast ratio as a selling point, so it's easy to compare the various contrast ranges offered.
Resolution refers to the number of image-producing pixels a particular projector uses to project an image; the greater the number of pixels that it uses, the greater the clarity and definition of the projected image. HDTV resolution, for example, is standardised at 1920 pixels in width and 1080 pixels in height. That's a total of more than two million pixels producing the image. The result is a sharp, high-definition image.
The image format or 'aspect ratio' of a projected image refers to the difference, or ratio, between the width and height of the image. Widescreen HDTV images, for example, have an aspect ratio of 16:9. In other words, if the image is projected to a width of 16 units, its height will be nine units. Older TV and video broadcasts have a much 'squarer' aspect ratio of 4:3. In addition, the aspect ratio of the video source also has to be taken into account. If a 16:9 format HDTV movie is being projected by a projector that has the same 16:9 format, it will be a perfect match. If the image source is some other source, such as certain DVD movies, it will likely have a different aspect ratio to the projector's 'native' aspect ratio. This means that, assuming the screen has the same aspect ratio as the projector, dark bands will appear at the sides of the image on the screen while it's displaying video of a different format.
How well a projected image fits the screen that it's projecting onto depends not only on the various aspect ratios of the source, screen, and projector, but also the physical distance between the projector and the screen. In some room or office situations, it may not be possible to have the optimum distance between the projector and screen. Rather than trying to fill the screen by moving the projector closer to the screen, which might not be convenient or practical, use the zoom feature if one is included. The image can be magnified, to an extent, by varying amounts. Using a zoom feature to magnify the image can improve the overall picture viewing experience considerably. Try different zoom settings but keep in mind that zoom can only enlarge the whole image. It can't change the aspect ratio of the image. Some projectors also offer lens tilt and shift options for raising the whole image or projecting slightly off centre. Different room or business locations have their own particular requirements.
As with all audio and video equipment, accessories such as extension cables, remote control, headphones, and more are also available for projectors. Two projector-specific accessories, however, are worthy of special mention: screens and lamps.
While any projector can project its picture onto a white wall or onto an office or classroom whiteboard just as easily as it can project onto a dedicated projector screen, the screen provides a more realistic movie-theatre experience for home projector owners, and a more professional looking set-up in office and classroom situations. Some screens have fold-away outer edges. This provides an excellent solution to the unsightly black edges that may surround the image when playing video sources that have a different aspect ratio to that of the projector. Effectively, the screen can be made to match the aspect ratio of the projected image simply by folding back the screen edges that are unused.
The most common types of projector use a lamp or bulb light source. Projector lamps, unfortunately, don't last forever. They have a working life of around 3000 hours as shown in the projector's specifications. Even if the lamp doesn't fail within that time, its brightness will gradually decrease over that period. Replacing lamps isn't cheap, but as the lamp is an essential part of the whole projector system; it's an unavoidable expense that has to be taken into account when buying a projector. Some owners recommend buying a spare lamp at the same time as the projector. It increases the overall cost of the system, but at least it avoids the shock of having to buy an expensive new lamp at a moment's notice if the original one suddenly fails. Projectors that use LED lamps don't suffer from this problem, and manufacturers proudly proclaim a working lamp-life of around 50,000 hours.
Finding a Projection System on eBay
Projection systems can be found on eBay without any trouble. Using eBay UK's homepage search function, the search term, ''projector'' returns a large number of results. It's an unsorted list, however. It contains projectors of all types, plus an assortment of projector accessories. That's why eBay provide a category system that enables sellers to list their projectors and projector-related items into relevant categories that are more easily searchable. The categories, plus a range of filtering options can be seen at the left side of the page following a search. Sound & Vision is the top-level category under which the majority of projectors are listed. Within that category, the sub category, DVD, Blu-ray & Home Cinema has the most relevant listings. Having conveniently grouped them, the filtering options can then be used to search for a specific type of projector according to, for example, minimum resolution and preferred format or by other criteria, such as maximum price, condition, (new, used or refurbished), and more.
For those looking for the ultimate in home-based audio-visual entertainment or a highly portable and convenient means of presenting business data or educational materials to groups of people, there are projectors that will do the job perfectly. If price is a barrier, there are still plenty that will do the job adequately. All that's required then is to find one and buy it. Given the range available, it's not difficult, and armed with a reasonable knowledge of the various features on offer, choosing a suitable and affordable projector becomes a far simpler task.