With more and more people setting up their own home cinemas, projectors are becoming common place in the lounge. Offering as large a screen as you want and only taking up minimal space it is an economical alternative to a large plasma or LCD television. Our buying guide outlines the points you will need to consider before you make your purchase.
Content
Aspect Ratio
The first thing to consider when buying a projector is what aspect ratio you want it to have. The aspect ratio is the ratio between the height and width of the image, a 4:3 aspect ratio means that the picture is 4 units wide and 3 units high. Usually the limit for your projected image will be width, so assuming equal width here are true to scale images of how the different types of projectors treat 4:3 and 16:9 content:
 4:3 projector showing 4:3 image |
 4:3 projector showing 4:3 image |
 16:9 projector showing 4:3 image |
 16:9 projector showing 16:9 image |
As you can see the image will be larger for 4:3 content on 4:3 projectors, and the 16:9 image will be equally large regardless of the projector’s aspect ratio. A common belief among home cinema enthousiasts is that 16:9 is better than 4:3. That is true if you only ever watch 16:9 movies, because then the image will fill the entire screen. However, not all movies are 16:9 format, old classics are 4:3 and some are more widescreen than 16:9. So why do people say that 16:9 projectors are better then?
- One thing is the black bars that will appear either over and under the image for a 4:3 projector, or left and right of the image on 16:9 projectors. Depending on the contrast capabilities of the projector and what type of screen is used, these bars will be different shades of dark grey for all projector types except CRT. When watching a movie, these grey bars can be annoying for some people so if they mostly watch 16:9 content the image will fill the entire screen and there won’t be any black bars.
- Another thing is how much of the projector’s resolution is used to show the actual image. The resolution of the cheapest projectors are 800x600 for 4:3 projectors and 858x484 for 16:9 projectors, so at this price, a 16:9 projector will give better resolution for 16:9 material. However, at the other end of the price range, the best 4:3 resolution is 1400x1050, which is much more than the native 16:9 projectors currently offering max 1280x720 resolution. What about in the middle of the price range then? There we find projectors with 1024x768 resolution, and it’s not uncommon for them to cost half compared to 16:9 projectors with the corresponding 1024x576 resolution.
So what aspect ratio should the projector have then? Basically it’s a matter of personal preferences. Do you want the image to be as large as possible both in 4:3 and 16:9 formats, then a 4:3 projector can be a good buy if you don’t mind the grey bars over and under the image. If you are on a tight budget and want the best resolution possible for widescreen material then a true 16:9 projector is probably what you’re looking for.
Display
There are several different display types with different picture quality and lens life; LCD, DLP and CRT are the most common:
- Cathode Ray Tube (CRT)
CRT projectors deliver a high degree of illumination and can project high-resolution video and data at up to workstation frequencies. Computer resolution can be as high as 2,000 lines. The main disadvantage of CRT projectors is that they are very big, and initial installment can take a couple of hours, but once installed, the image is simply stunning. CRTs need to be adjusted for each resolutions and frequency you intend to use, but this is simply done by copying the settings from one memory bank and making a few adjustments. - Digital Light Processing (DLP)
A DLP projector uses hundreds of thousands of tiny mirrors, each smaller than one-fifth of a human hair. Each mirror is operated by a littler motor that tilts the mirror to make the light either pass thru or be blocked. Colours are generated by a spinning wheel with three or more colour segments. DLP projectors offer high brightness and contrast, but they are more expensive than LCD projectors. Another big disadvantage is what is refered to as the “rainbow effect” – since colours are shown separately and alters between red, green and blue many people get headaches or even nauseous when watching an image displayed by a DLP projector. Newer models have a colour wheel that spins faster or that has more colour segments to reduce the flickering. - Liquid Crystal Display (LCD)
LCD stands for liquid crystal. Polysilicon TFT LCD is a popular LCD technology for the top of the line LCD projectors. Three monochrome LCDs are placed in each of the three color light paths inside a projector, one each for Red, Green, and Blue. This results in increased color saturation, with contrast ratios above 200:1. LCD projectors are relatively cheap and have good resolution, making it a good choice for most purposes. The main disadvantage is that black will never be completely black, something the manufacturers try to compensate for by tweaking colour saturation settings.
True Widescreen
A projector with true widescreen is a projector with 16:9 native aspect ratio (the name of the resolution starts with a W).
Resolution
The sharpness and clarity of the picture on the screen is determined by a projector's resolution. Resolution refers to the sharpness of the image projected, as expressed in pixels (the higher, the better). When it comes to projectors however, the thing you want to pay attention to is the "Native Resolution." This refers to the true resolution (i.e. non-compressed, non-expanded) of the projector.
- SVGA, or "800 x 600" – This is a popular resolution today, because most notebook computers are SVGA. Matching the projector resolution with the computer resolution will produce the best results.
- XGA, or "1,024 x 768" - XGA projectors are generally more expensive, and are the second most popular resolution format. Many of the newest products are coming out in XGA. They are getting more popular as prices drop and the use of XGA notebook computers increases.
- SXGA, or "1,280 x 1,024" – SXGA products are high resolution, and notably more expensive than XGA. These products are targeted for high end personal computer users and low end workstation users. They are used primarily for command and control, engineering and CAD/CAM applications where acute resolution of small details is important.
- UXGA, or "1,600 x 1,200" – UXGA is for very high resolution workstation applications that are detail or information intensive. These are expensive projectors that support a broad range of computer equipment. Relatively few products on the market have this native resolution.
- WVGA, or “858x484” – The lowest true widescreen resolution available on the market. This is most commonly found in lower price range projector.
- WXGA, or "1280x720" - A very high true widescreen resolution well suited for home cinema use. With a true widescreen projector you use the entire resolution to show the actual image when viewing movies in widescreen format, without the black bars over and under the image that you otherwise get.
Most projectors automatically accept images that are of other resolutions than the native resolution of the projector. The resulting image is scaled to fit the native resolution of the projector using a variety of scaling algorithms. Not all projectors use the same compression algorithms; therefore, the quality of compression can vary. The nature of compression in a digital device means that some image content is lost. For CRT projectors you can’t really say it has native resolution, since they don’t have a panel like DLPs and LDCs have.
Many different models are now available giving varying proportions of fridge/freezer space so before you buy think about the types of food that you buy:
- If you shop regularly for fresh food and only really use the freezer for ice cubes and other odd items you may need a model with a larger fridge area and smaller freezer. If your shopping tends towards lots of ready meals, prepared foods and bulk buying a larger freezer area will suit you better.
- Knowing the actual capacity of each section will give you an accurate idea of size but look inside. A fridge section will have various areas within it for dairy, chilled food, bottles etc. Some will even have a chilled drinks dispenser and as you might expect, these types of extras tend to come at a higher price. Check these to see if the layout inside is to your liking, or if it can be altered to suit you.
Storage capacity is measured in cubic feet or litres. The smallest fridge freezers can offer around 4 cubic feet of storage (around 120 litres), and can be quite adequate for single people. A total capacity of around 9 to 10 cu ft (around 300 litres) is generally adequate for most families, although much larger sizes of fridge freezers are available providing ample long term storage.
Brightness & Contrast
Projectors come in a wide range of light output. All other things being equal, the brighter the projector, the more it costs. When it comes to "optimum brightness" the rule is simple: get the brightest projector you can afford.
Brightness is measured in ANSI (American National Standards Institute) lumens: the brighter the projector, the higher the ANSI lumen rating. In today’s market, projectors can be grouped by ANSI lumen output as follows:
- Less than 1000 lumens – these are the lowest light-output projectors available today, and they are typically the least expensive. If you are on a tight budget, there are a number of products in this category that may be perfect for your needs. Keep in mind that the low light output means that you will want to make your presentations in a dark or dimly lit room so that the image on the screen is not washed out by ambient room light.
- 1000 to 2000 lumens – this lumen range is a step up in performance and price. There are many SVGA and XGA products in this class to choose from. These machines are suitable for normal business conference room and classroom use. Presentations should be done with the room lighting reduced somewhat for best screen viewing, although a totally dark or dimly lit room is usually not necessary.
- 2000 to 3000 lumens – this represents the high-performance range of the portable and semi-portable projectors. Products in this class are suitable for large conference rooms and classrooms. They offer more flexibility in terms of ambient room light, since the image is bright enough that a reasonable amount of room light can be tolerated without washing out the image. They also offer more flexibility in terms of audience size since they can illuminate a larger screen without much loss of image quality.
- 3000 lumens and up – the ultra-bright projectors are in several performance classes unto themselves, ranging from 3000 up to 12000 lumens or more. Prices of these products also cover a wide range depending on other performance characteristics. They are used in a variety of large venue applications, including board rooms, conference rooms, training rooms, auditoriums, churches, concerts, nightclubs, and so forth.
Contrast is measured as the ratio between the light intensity of the brightest and the darkest point of an image. High contrast values improve readability and ergonomics. Too low contrast ratios cause darker shades to be displayed as black. Room light substantially impacts contrast ratios. If you intend to use your projector with the lights on, consider projectors with very high contrast ratios.
For CRTs, a high contrast is accomplished by not lighting up parts of the phosphor, while DLPs and LCDs have to block out the light where darkness is wanted. This is physically impossible as some light always slips through. However, it is physically not possible to do this perfectly - some light will always seep through.
Image Size & Projection Distance
Both image size and projection distance are most often physically bound by the size of your room. How big the image should be is very much a matter of personal preferences, but a general guideline is that the distance from the screen to your viewing position should be about 1.5 to 2 times the width of the screen. This will reduce pixellation and give you a more pleasurable viewing experience.
Many projectors have optical zoom possibilities allowing you some freedom when mounting it and still giving you the desired image size.
Dimensions
Another consideration in selecting the ideal projector is its dimensions. If you are on the road a lot, you probably want the lightest, most portable machine available that is adequate for your application needs, then look for a projector under 2 kg. If weight is not an issue then go for a projector with better qualities such as display type, resolution etc.
Keystone Correction
If the projector isn't placed correctly towards the screen, the image will be trapeziod. With keystone correction, the projector can still project a rectangular image. The best is optical keystone correction, since this will not reduce image quality like digital keystone correction does. With digital keystone correction, one or more lines at each side of the projector is used to tilt the image so that the resulting image will be square at the screen.
Warranty & Lamp Life
Most manufacturers offer a warranty of 1-3 years for the projector, but hardly anyone has more than a three month warranty for the lamp. Lamp life is defined as the average time span for the brightness of the lamp to be reduced by half; it does not refer to the warranty period for the lamp.The replacement lamps are quite expensive, so when choosing between projectors with otherwise similar specifications, the one with better lamp life will be cheaper in the long run.
Audible Noice
This is a measurement of how loud the fan noice is from the projector. Sometimes the projector can be set to run in low brightness mode, wich will lower the fan noice and often also prolong lamp life.
Speakers
Many projectors have integrated speakers. They should not in any way be seen as an alternative to full size speakers in a home cinema, but they can be sufficient for presentation purposes.
Power Consumption & Lamp Effect
A projector with higher brightness will often have higher power consumption and also lamp effect. They also generate heat that needs to be dealt with by the fan, and more heat means that the fan will have to run at higher speeds with higher audible noice as a result.
Bandwidth
The bandwidth is the amount of data that the projector can handle per second. To calculate an estimate of the bandwidth needed for a given resolution and refresh rate, you can use the following formula:
- Bandwidth = 1.05Y*1.3X*R
- Where Y is vertical resolution, X is horizontal resolution and R is the refresh rate. That gives an approximate bandwidth of 87MHz for 1024x768@85Hz and 145MHz for 1280x1024@85Hz
Frequency
The speed that a projector draws a single scan line, called the "horizontal frequency," is measured in kilohertz (kHz). The process repeats, painting line after line, until the screen is filled.
The speed that a projector draws an entire screen, called the "vertical refresh rate" or "frequency," is measured in hertz (Hz).
Connections
Most projectors have VGA (computer d-sub), S-video and composite (a cable with a yellow connector) inputs. Component video has the greatest picture quality, followed by s-video and then composite as your very last option. Many offer additional inputs such as DVI for digital transfer from your computer, component video and audio input. Some also have wireless connectivity for greater flexibility.
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