TECHNOLOGY
Sales of bulky old CRT (Cathode Ray Tube) Monitors have now been overtaken in by TFT-LCD screens. While CRT remains cheaper with comparable image size (a 15” LCD is equivalent to a 17” CRT), CRTs are on the other hand three or four times more cumbersome on average than LCD and consume approximately three times more energy.

SCREEN SIZE
The size of the screen you buy will of course very much depend on what you need the screen for. Displaying the same quantity of visual information on a screen of a bigger size makes it possible to improve eye comfort.
An LCD offers a real image size equivalent to that of a CRT which has a diagonal of 2” more: the standard of monitors LCD is thus now 17", which gives a usable real screen size to a 19” CRT.

SUPPORTED RESOLUTIONS
The size of screen corresponds only to the size of the image, not to the quantity of information (in dots, or pixels) able to be displayed: thus, with equivalent resolution, two screens of different size will display exactly the same number of pixels and thus the same quantity of information. In addition, while it is possible "to push-up" the resolution of a CRT (by increasing the refresh rate to avoid a phenomenon of flutter), an LCD should be used only in its native resolution, i.e. that corresponding to the real number of pixels present on the panel (there is no point increasing the resolution of the signal beyond what the screen is able to display… this in fact will only result in a degradation of image quality).

SCREEN FORM-FACTOR
Most computer monitors have until now been produced in a 4:3 format, but we are seeing an increasing number of models on the market in a 16:9 format. These monitors (exclusively using LCD technology) offer the advantage of being compatible with DVD images, but in addition to this, within the framework of office applications, they make it possible to post the Office™ bar developed by Microsoft, without reducing the usable working surface of the screen.
Another feature which has come with the LCD monitor is that of “pivoting” which makes it possible to swivel the screen through 90 degrees to put it into portrait mode and thus display a full size, upright US-Letter size document.

COLOR RENDITION AND CONTRAST
The number of colors a monitor is able to display is important if you’re using it for graphics or even for watching video images: more the range of colors is broad, better the image quality will be. For this kind of thing, CRT screens have still generally been better than LCD, but more recently, LCD has benefited from notable technological improvements, making it possible for certain models to produce excellent quality images. In the same way, contrast ratio of governs the "legibility" of the image, while making it possible to better distinguish the details when they are in similar colors. These criteria, of course, are of little importance for traditional office use, but are essential for applications like CAD/CAM, graphics, video assembly, etc.

QUALITY OF VIDEO RENDITION
During the display of moving images, the response time becomes an essential criterion.
CRT monitors do not have too many problems here (although the weak link will probably be the graphics board), while LCD monitors present, according to the models, very disparate performance levels.
Once again, if it is a question of using the monitor for traditional office applications, this criterion is not important… However, if the monitor is used for watching video or moving 3D simulation, it is very important to ensure the screen has a good refresh rate. This is to ensure that fast moving images on the screen will not generate visual artifacts (trailing…). Most modern LCD panels have a refresh rate better than 16 m/s, however what they don’t tell you is that it’s more important to calculate the response time between two different gray levels, which can only be done in a test lab, and this is rarely, if ever cited by manufacturers. Make sure you test the various screens you’re looking at with fast moving images, and don’t be hypnotized by those lovely slow moving demo videos they us in many shops.

VIEWING ANGLE
According to whether you look at a screen face-on or not, the quality of the image, in particular contrast levels can change.
While being placed directly opposite the screen, one is assured that the visual result will be optimal but the more off-center you are, the more faded the picture is likely to become, depending on the LCD technology used (see technology section).
In theory, this criterion is not essential for office applications, since the user by definition is placed in front of his or her screen.
However, if several people want to look at the screen at the same time (i.e. watching a video), viewing angle will be a major deciding factor.
On the other hand, if you’re using the screen in a situation where you don’t want inquisitive eyes to stray onto your screen, polarizing filters are available which considerably reduce viewing angle and ensure that only the user placed behind the screen can see what’s on it.

CONNECTIVITY
Traditionally, a monitor is connected to a computer by a VGA cable which conveys, in analog form, the 3 (Red-Green-Blue) components of the computer image.On the other hand, if the monitor and graphics board allow it, it is possible to substitute this for it a DVI (DIGITAL video interface) connector which transmits 100% digital data and thus guarantees a better image quality. In addition, certain screens offer additional connector interfaces (USB, headphone, microphone, etc.) which may, in certain cases, prove to be very useful.