AUDioImages

When to and not to.
The biggest question mark on projectors is if they will suit your lifestyle. For instance is this your day? - you get up and turn on breakfast TV, someone at home all day leaves on the TV for company, you come home and even though you don't really have anything in mind to watch, you put the TV on as background - if this is you then a projector should not be your choice. A projector has a lamp which has a finite life. Anywhere from 2000 hours upwards (to as many as 6000 hours on some models) is usual. When this is worn out then you will need to replace it with a new one. The projector its self will last many many times longer, but the lamp is a wearing item. Lamps can cost from £150.00 to £650.00 So to leave a projector running when your not really watching is a pointless waste of the lamps life, and if you do like something on as you do your chores at home then you can see that a projector would be the wrong choice. Also, a projector, by its very nature likes to be in a darkened room. That is not to say that you need to live life in a pitch dark room thinking of war time blackouts. But, direct light onto the projection screen will spoil the show, so be prepared to offer at least some kind of direct light dimming, such as blinds or curtains for daytime viewing.


Home Cinema projectors V's Data projectors.
Projectors come in many different types, but we should distinguish between one that was made to produce data pictures from a computer and ones that produce home cinema pictures. Data projectors quite often have much brighter light output (measured as Ansi-Lumens), they may also have higher resolution rates. This makes them great for viewing computer graphics on but is not ideally suited for home cinema. However, home cinema projectors shouldn't have to much light as this gives very poor definition on large areas like looking at a sky view, where the detail of clouds is lost because of too much light. Home Cinema is also nearly always in a 16:9 format as opposed to Data 4:3. Home Cinema models have much better video processing boards to avoid shearing of the image under fast moving reproduction. Contrast ratio is also very important, the figure usually given indicates the difference between full on (most light) and full off (absence of light). The higher the figure the better as this gives much blacker black levels, although this is no guarantee of which projector is best. Only a general indication.

Throw ratios
All projectors have a throw ratio, and it's worth being able to work this out to decide if it will fit your room. A throw ratio is the distance the lens of the projector must be from the projection surface of your screen to get a fixed amount of picture width. For instance if a projector had a projection ratio of 1:1.5. That is say that you come back 1.5 feet (or metres, the measurement type is irrelevant) to get a 1 foot wide picture. 3 foot back to get 4.5 feet of picture ad so on. In reality, most projectors have a range of throw adjustable at the lens. For instance one of the most popular projectors has a range of 1.52:1 to 1.92:1


Technologies.
There are four types of projector available, with the majority being just two of these.

LCD is perhaps the most widely known of. Imagine that you have a computer laptop display on miniature (maybe just 0.7 of an inch square), but the display has no back to it. Instead the light shines through this and creates a picture on your wall. In the case of LCD projectors they will most likely have three of these tiny panels (One Green, One Red & One Blue) and the light converges on a central point inside of the projector to form a full colour image.

DLP The most successful at this time for home cinema is DLP (Digital light processing) and is an invention by Texas instruments. On first explanation of this technology it would seem to have been invented by a madman. It is complex and seems to be open to breakdown. Nothing could be further from the truth however. DLP has proved its self to be very reliable indeed, even more so that LCD. A brief explanation would go like this. The lamp shines through a colour wheel on to the DLP chip. The chip is made up of tiny hinged mirrors. The chip its self is again very small (less than an inch) The resolution that you read about - say 1280 by 720 - is how many mirrors populate the chip - in this case 921,600 of them. These mirrors are packed very close together (much more so than the cells on an LCD chip) which gives a picture where it is much more difficult to see how the picture is made up. The colour wheel is a thin wheel made up of segments containing at least four pieces (One Green, One Red, One Blue & One clear for registration purposes). The projector then makes the mirrors flap open to reflect light when the correct colour passes by. As a technology it is quite frankly on paper as mad as a box of frogs. But it really works. In order to do away with something called rainbow effect (where turning your head will show you a flash of rainbow colours on screen) most projectors have multiples of segments of colour - such as a seven segment colour wheel. Some mirrors also now have a special coating on them which increases the contrast ratio. You can also at the higher end of DLP's get three chip DLP's, where there is no colour wheel at all, but instead there are three mirror devices, one coated in each of the primary colours. These can give a stunning picture and currently what most people would see as state of the art.

CRT is the oldest of the current technologies and utilises three small CRT tubes (again one for each of the primary colours, 9 inch tubes being the biggest) which then converge on your screen to form the picture. Most people remember seeing one of these in their local from years gone by, shinning up onto a fixed screen just in front of the lamps. These are much improved over those days, and it is possible in fact to get the most natural picture from one of these that is available. However, their down side is they are huge, expensive, and can take a very long time to set up and then mustn't be moved again afterwards.

D-iLa technology is quite new and offers some of the benefits of superb depth from the CRT type projectors but at the higher light and resolutions of DLP. Developed by JVC and utilising LCD in a totally different design to that of standard LCD technology, D-iLA could be a future well worth keeping an eye on. 

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