The humble monitor is probably the most important computer peripheral in a system, simply because it is used all the time. It is the basic way computers communicate with users, conveying precious information. But poor or unsuitable displays can reduce productivity, cause headaches or, worse still, emit harmful radiation.
Choosing an ideal monitor for your application can be as tough a decision as buying the computer itself. What size should you opt for? Do you need built-in speakers or video cameras? Is the conventional cathode-ray tube the right choice, or should you opt for a thin-panel screen? What level of performance do you need for your application, and are the stories about radiation and safety just scaremongering or genuinely serious issues?
In this article we intend to answer these questions and concerns. We look at five typical applications and show which display technologies and specifications are the most suitable for them. Also, for each application, we've chosen one outstanding product to indicate what you should be looking for.
Those who want to learn more about the technology involved in manufacturing monitors will be interested in our explanations at the end, while our discussions on safety and radiation standards should concern everyone.
Large-volume, low-priced, small display for general use
The most common monitors worldwide are made by Compaq and IBM, simply because of the vast number of complete systems each company sells. Until recently, the 14in VGA monitor dominated the entry-level market. However, with widespread migration from DOS to Windows and other graphical user interfaces, higher quality, slightly larger models are seen as minimum requirements.
According to research organisation Romtec, for the first time ever, sales of 15in monitors overtook those of 14in displays this year in the branded market, where a typical buyer is upgrading. In the indirect OEM market, where the monitor is bundled with a PC, there is still a bias towards 14in models. But the situation is certainly changing.
If you are looking to buy a small, cheap display in bulk for general use, go for a model that can run Windows above VGA resolution without flicker, and which complies with safety standards to cover you well into the future.
Avoid 14in monitors; instead, opt for a 15in which can comfortably display 800x600 pixel resolution (also known as SVGA), in a non-interlaced mode at above 70Hz refresh rates for a flicker-free display. It should also automatically powerdown, and conform to at least MPR-II safety standards - or even the more stringent TCO-1992 for the really conscientious manager.
Samsung Syncmaster 15Gli
At some point, most companies will have to face the job of choosing a large volume, low-price, small display for general use.
In the days of DOS, it was possible to skimp on quality and even go for monochrome displays. Today, most computers run a graphical user interface such as Windows. Despite being compatible with standard cheap VGA monitors, it is designed to give optimum performance on something better.
Before baulking at the expense of buying tens or even hundreds of such displays, it is important to consider recent developments. Nearly all monitors can automatically powerdown when not being used. This reduces your electricity bill, as well as being environmentally friendly.
Also, if it is a while since you last bought a fleet of budget displays, you should bear in mind that several safety standards on ergonomics and emissions have either become law or soon will be. And it is important to appreciate that a poor display can result in reduced productivity.
The 15in displays from Sony, NEC and Philips are particularly impressive.
However, it is Samsung, with its best-selling Syncmaster 15Gli monitor, which we recommend to the bulk buyer.
Samsung is the third largest electronics company in the world. It is the world's largest supplier of computer monitors and was the top-selling brand of third-party monitors in the UK during the first quarter of 1996, with a market share of more than 25 per cent by volume.
The Syncmaster 15Gli is a superb-quality 15in monitor, conforming to MPR-II safety standards and VESA DPMS for automatic powering down. The tube displays a sharp, clear, flicker-free image at resolutions of 640x480, 800x600 and 1,024x768 in non-interlaced modes at up to 75Hz.
Verdict: plug-and-play, decent on-screen controls and cabinet design make the 15Gli a perfect choice for any 15in application.
High-quality display for the demanding executive user
A competent 15in monitor will satisfy most people. But more demanding users who want greater performance for specific applications, or who just like the idea of a superior model, should look at an above-average 17in model.
Working at higher resolutions means you can fit more information on your screen, such as viewing extra cells in a spreadsheet, without having to scroll around incessantly. However, as resolution increases, all Windows text and objects shrink, making them illegible on a smaller display.
The answer is to go for something larger, and a decent 17in monitor is perfect for operating at 1,024x768 resolution - and sometimes higher still.
Again, make sure it can display this resolution in a non-interlaced mode above 70Hz for a flicker-free image.
Multimedia users may be interested in a model with built-in speakers and microphone, or even a video camera ready for video conferencing, without countless extra boxes and wires cluttering up the precious desktop.
Once again, the major names stand out in this category. NEC, Sony, Iiyama and Mitsubishi offer superb models, but the Nokia 447Xavc is particularly impressive and is the top recommendation.
Finland-based Nokia has always been at the forefront of high-quality monitor design. Its innovation has resulted in one of the first monitors with built-in stereo loudspeakers, subwoofer, microphone, and even a video camera.
The 447Xavc features a Sony Trinitron 17in tube with a 15.7in viewable area. It's an extremely high-performance display, which handles high resolutions up to 1,280x1,024 pixels, non-interlaced at up to 85Hz, for an incredibly steady image. These high resolutions are perfect for viewing large amounts of information in one go.
The 447Xavc conforms to MPR-II and the strictest TCO-1995 safety standards. Also, it can automatically powerdown using VESA DPMS.
Even given its outstanding image quality, the 447Xavc's most impressive feature is its multimedia capability. It boasts a built-in microphone, two 2Watt loudspeakers, a 10Watt subwoofer and, best of all, a colour CCD video camera. The camera is directly below the screen in the centre of the case. It can be tilted up and down, and works in the PAL system for Europe, or NTSC in the US.
The CCD camera feeds its signal to a standard composite video RCA jack at the rear of the monitor. This can be connected to suitable video conferencing systems or just an additional display.
Verdict: the 17in 447Xavc is perfect for power users who also want video-conferencing facilities - without wires and separate boxes cluttering up the workplace.
High-quality display where space, low interference or design is paramount
The ageing cathode-ray tube (CRT) may produce decent images at low prices, but it takes up an enormous amount of space. Also, it often emits radiation which can interfere with sensitive electrical equipment. Fortunately, there are alternative display technologies.
You can now buy thin-film transistor (TFT) flat-panel displays, as found on many high-end notebook computers, for desktop users. They are obviously thin, often measuring only a couple of inches deep - compare that with your CRT monitor.
Quality is extremely high and, recently, performance and image size have started to compete with CRTs. Some panels run at up to 1,024x768 resolution and boast 15in viewable diagonals. But you should bear in mind that an average 17in CRT monitor only has a viewable diagonal of just over 15in.
The only drawback is price, with a TFT panel display costing at least four times as much as a CRT which does the job just as well. However, some applications demand panel displays or can easily swallow the cost.
For instance, desk space in City dealing rooms is at a premium, and brokers need access to as much information as possible, so a large screen with a thin display is ideal. Not only are TFT panels small and light, but they don't suffer as much interference as CRTs, so they are perfect for many government or military applications. They're also good looking, which makes them ideal for image-conscious company receptions and meeting rooms.
Taxan Crystalvision 650
Taxan doesn't make its own tubes or panels, but it is the number-one seller of third-party monitor units in the UK. Although it has been manufacturing flat-panel monitors for some time, its latest model really caught our eye.
Unconditionally recommended in this category is its Crystalvision 650 monitor, which boasts no less than a 14.5in colour TFT panel. What's more, the entire 14.5 inches are viewable. This makes it comparable to many 17in CRT monitors, which may only have an actual viewable area of 15 inches.
However, while the image size is comparable to a 17in CRT, the Crystalvision is a fraction of its depth, at only 2.5in.
Taxan's panel offers up to 1,024x768 resolution in flicker-free modes for a truly great-looking image. It's also the only panel so far to be certified as TCO-1992 compliant. The Crystalvision 650 is Windows 95 plug-and-play compatible and supports VESA DPMS power-saving. However, it uses only 27Watts when in operation.
The Crystalvision 650 even features stereo loudspeakers.
In addition, it accepts the analogue output of a standard video card, whereas many panels in the past have required a dedicated video card, which costs extra and is inconvenient to fit.
Verdict: with a 2.5in thin display, all-round good looks, 14.5in colour TFT screen and a superb flicker-free image, the Crystalvision 650 is an excellent choice for style-conscious users who are short on space.
Large-screen display for making presentations to several people
Increasingly, people are using computers to make presentations. But you need a large image when presenting to an audience. There are several ways to do this.
The first, and probably least elegant solution, is simply to use a huge television-type monitor, with a computer VGA input. However, this has drawbacks: the resolution is limited to 640x480 VGA, image quality is usually poor and the whole set-up looks rather clumsy.
The second option is to use a projector and screen. There is an extensive range of video projectors, based on either a TFT flat panel or a CRT, which offer high-quality resolutions from 640x80, right up to 1,280x1,024 and beyond, if your budget can stretch to it.
Alternatively, a small panel can be placed between a bulb and lens to project a high-quality image in precisely the same way as a slide projector.
These LCD projectors can be expensive, but are quick and easy to set up, which makes them handy to carry about. For even greater portability, there are larger, and more expensive panels on the market, and these can be placed directly on an existing overhead projector (OHP). Some companies combine a panel and OHP into a single unit.
You could always opt for the three-tube CRT projector. This offers excellent quality at a reasonable price, although installation is laborious.
Proxima 9100 Desktop Projector
Whatever size of group you are presenting to, you'll want to be backed up by a large, clear image. Therefore, in this category, we recommend the convenience and quality of a TFT panel-based projection system.
It's possible to fit a small panel into a slide-style projector, or use a larger panel placed on an existing OHP. But we have plumped for a combination OHP and panel, which will knock the socks off your audience.
Proxima is extremely experienced in the field of presentation hardware.
Its latest Desktop 9100 high-resolution projector is impressive enough to earn our top recommendation in this category.
The 9100 is based on a compact OHP with a colour TFT panel. The 575Watt metal halide bulb (which lasts about 700 hours) can project a bright image from 132cm to 409cm diagonal, at a distance of 1.2m to 4.3m. The panel operates at 1,024x768 resolution but can scale down to 640x480 or up to 1,280x1,024.
The Proxima 9100 includes the Cyclops interactive pointing system, a remote-control unit and software which allows a presenter to control the computer's pointer without touching a wired mouse. The 9100 even has built-in, rear-facing 3Watt stereo speakers for modest multimedia presentations.
The 9100 is a good-looking system, with the optical reflector section folding down for storage or transportation - when shut, it measures 351x503x185mm.
Proxima and many of its competitors are distributed in the UK by GBI, a company with extensive knowledge of presentation systems. Hardware isn't cheap, so it is worth talking to such experts and seeing demonstrations before you buy.
Verdict: the quality of this TFT panel-based projection system from Proxima will hit your audience right between the eyes.
High-quality, large display for single-user graphics and CAD applications
Computer aided design (CAD), desktop publishing (DTP), and graphics users demand the highest quality displays of all. The nature of their work demands the use of very high resolutions and high refresh rates, and requires that colours are reproduced accurately with the minimum of image distortion.
Traditionally, such users have opted for 20in or 21in CRT monitors, running at resolutions of 1,280x1,024 or even 1,600x1,200 pixels; also, it's not uncommon to find refresh rates of over 80Hz to ensure a truly flicker-free image.
These large tubes allow whole A4 or A3 pages to be viewed at actual size.
Many users opt for Sony Trinitron or Mitsubishi Diamondtron tube technologies, which present a brighter and more vibrant image (see 'How CRTs work', page 127).
Accurate colour reproduction and matching from scanner to screen to printout is extremely difficult, but is very often accomplished using additional software; both Kodak and Agfa offer excellent colour-matching software.
Distortions and lack of uniformity across the screen can cause problems for graphics and CAD users. To provide a solution to this, Philips has recently launched its Cyberscreen technology, which can adjust many regions of a 21in tube independently of the others. Combined with feedback, hardware and regular calibration, Cyberscreen offers an expensive but extremely accurate system.
Mitsubishi Diamondpro 91TXM
Graphics, DTP, pre-press and CAD users want large monitors for two main reasons. Firstly, they want to operate at ultra-high resolutions of up to 1,600x1,200 pixels, which is only practical on a physically large screen.
Secondly, they want to display A4 and A3-size documents at 1:1 actual size. Unfortunately, 21in flat-panel screens are still in development, leaving this category to the traditional cathode-ray tube.
Graphics users demand accurate colour representation, and the level of brightness rarely found outside Aperture Grill tube designs (see 'How CRTs work', on this page). Aperture Grill technology was developed by Sony for its Trinitron designs, and more recently adopted by Mitsubishi with its rival Diamondtron technology.
Although Sony Trinitron tubes are superb, they are expensive compared with Mitsubishi's Diamondtron, which offers the additional advantage of a 21in model as opposed to Sony's top-sized 20in model. In this category, the Mitsubishi Diamond Pro 91 TXM 21in monitor is recommended.
It boasts a maximum resolution of 1,600x1,200 non-interlaced at 75Hz, and is perfectly happy operating at lower resolutions. The image is as bright and vibrant as is expected from an Aperture Grill tube.
It suffers little to no distortion or lack of uniformity, which is quite impressive for such a large display. The cabinet is also remarkably small for a 21in, measuring 500x490 x488mm.
The 91TXM is MPR-II and TCO-1992 compliant, and can automatically powerdown with VESA DPMS and EPA Energy Star. There are two sets of video inputs at the rear. These allow for two PCs to be connected simultaneously and switched between by the user.
Verdict: the Diamondpro 91TXM is an excellent choice for large-screen graphics or CAD applications.
How CRTs work
A colour cathode-ray tube is like a huge glass bottle with electron guns in its neck which fire at the screen in the bottom. The screen is covered with a matrix of dots, each consisting of three blobs of coloured phosphor - one red, one green and the other blue.
The three electron guns are aimed and fired at their respective blobs, and each is illuminated to a greater or lesser extent. The phosphors in a group are so close together that the human eye perceives the combination as a single coloured computer pixel. A metal mask separates each dot to minimise 'overspill' where the electron beam would otherwise illuminate more than one dot.
Magnetic fields are applied to drag the electron beam to strike any point on the screen. The beam starts in the top left corner (as seen from the front), scans across to the right, drops down a line and starts again at the left. This is repeated until an entire screen is drawn, at which point the beam returns to the top and starts again.
The number of times a complete screen is drawn per second is the refresh rate, measured in Hertz (Hz). The higher the refresh rate, the less flicker on the screen, up to a point where the brain perceives it as perfectly steady. A refresh rate above 70Hz is considered flicker-free.
Some monitors draw every other line, for example, 1, 3, 5 and so on, until the screen is full, then return to the top to fill in the even blanks.
This process is known as interlacing and leads to a flickering display.
With a non-interlaced monitor, every line is drawn before returning to the top for the next frame, so there is a steadier display.
The majority of computer monitors use circular blobs of phosphor, arranging them in a triangular style. These groups are known as triads, and the arrangement is known as a dot-trio design. However, there are alternatives.
In the 1960s, Sony developed a tube technology known as Trinitron. This involved coloured phosphors being laid down in uninterrupted vertical stripes. The mask separates entire stripes instead of each dot, and is known as an Aperture Grill. The screen area is taken up by the mask, so more of the phosphor can glow. This leads to a brighter, more vibrant display.
The downside is that either one or two very fine wires must be run horizontally across the display to hold the Aperture Grill in place. If you look closely, these are just visible.
When Sony's copyright expired, Mitsubishi developed its own version of Trinitron, called Diamondtron, using a similar Aperture Grill mask but with three electron guns instead of Sony's one.
Recently, NEC has developed monitors using the popular slotted mask design of many TV sets. This features elliptically-shaped phosphors grouped vertically and separated by a slotted mask.
It exposes more phosphor than a conventional dot-trio design. The result is not quite as bright as an Aperture Grill, but more stable, and brighter than the dot-trio.
How panels work
Flat panels are common on computer notebook displays. But many manufacturers and users are now realising that panels make great displays for desktop computers for a variety of applications, described here. But how do they work?
Two panel technologies are widely used, DSTN (double supertwisted nematic) and TFT (thin-film transistor). The cheaper DSTN panels, also known as dual-scan, are based on the liquid crystal displays (LCDs) found in digital watches.
An LCD consists of layers of crystals, sandwiched between films of glass.
A grid of electrical conductors represents each computer pixel, and changes the direction of the adjacent crystals when switched on. Polarising filters prevent light from passing through the oriented crystal, which results in a dark pixel.
Unfortunately, switching on one pixel usually affects those around it, causing a bleeding effect. TFTs, also known as active-matrix, use the same conducting grid, but feature a transistor at each pixel, which prevents bleeding.
Each pixel requires three transistors for red, green and blue filters, which results in an enormous number of transistors, especially at high resolutions.
If any transistors aren't perfect, they are immediately noticeable as blank 'dead' pixels. This level of perfection on a high-resolution, large panel accounts for their costliness.
Safety and emission standards
Many people spend hours in front of a computer without giving a second thought to safety. A monitor consists of extremely high-voltage electron guns. These fire streams of electrons sufficiently hard at a target of phosphors, that they glow brightly enough to produce an image. Those same guns are pointed directly at your face, typically for several hours a day, and are understandably of great concern.
Several safety bodies measure emissions and set standards which monitors must meet. The CE mark, which became law in the UK on 1 January 1996, forced electronics companies into more stringent testing methods. However, in the last few years, monitor manufacturers have already conformed to a range of safety standards driven by Sweden and the US.
First is the now ubiquitous Swedish MPR-II of the early 1990s, which reduces electrostatic emissions. The stricter Swedish TCO-1992 standard demands stiffer levels for emissions, as well as meeting the EN60950 international standard for electrical and fire safety.
The most recent and strictest of all, the TCO-1995
standard, also addresses environmental and recycling concerns. Each system adds more to the cost of a display, although MPR-II is considered a bare minimum.
Monitors also use large amounts of power, and are frequently left on while not in use. VESA's DPMS system allows a compliant video card and monitor to automatically powerdown, typically to 25Watts in standby, then below 8Watts in suspend mode. EPA's Energy Star system powers down to below 30Watts. Both systems are in wide circulation, and automatically act on user-definable periods of inactivity.
Other monitor technologies
Multimedia facilities are now quite common on many PCs. It is possible to conveniently incorporate stereo loudspeakers, a microphone and, in some cases, a camera, ready for video conferencing, into what are known as multimedia monitors.
Most built-in speakers are only suitable for basic sound reproduction.
If you are serious about sound, you should still opt for decent external speakers, which can also be properly magnetically shielded.
On-screen image correction controls are becoming increasingly common.
These are superimposed graphics which appear on the screen, obscuring parts of the main image, usually indicating what you're about to adjust.
It's just the same as modern TV sets superimposing, for example, a volume bar when you're turning the sound up or down.
There's no standard for on-screen graphics.
Consequently, there's a huge range of icons, bars, colours and sizes out there. Some are much better than others.
However, the whole point is to make adjustments intuitive and fast. That's very much a combination of how the display interacts with the buttons on offer.
You would think that all you have to do to get a monitor working, is plug it in and switch it on. In reality, a monitor will only be able to display a specific range of signals, and will come up blank or even damaged if it's supplied with anything else.
On the other hand, erring on the side of caution may result in you not making the most of your monitor's capabilities.
VESA has come up with a standard for plug-and-play monitors, which should communicate the display's capabilities, through the graphics card, to the operating system. Known as DDC, in theory, it should allow your system to figure out and select the ideal settings. But in practice, this depends on the combination of hardware.
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