The CRT is the principal component in a monitor, indeed the quality of the picture is determined by the quality of this component above all others. It is essential, therefore to know the main specifications of a CRT. 

1. CRT Size
This is the actual size of the CRT measured from opposite corner to opposite corner. It, unlike the maximum viewable size, is not a measure of the viewable screen area, it includes the margin hidden under the case of the CRT. 

2. Maximum Viewable Area
This is a measure of the actual part of the screen that is viewable, like the CRT size it is measured from opposite corner to opposite corner. When purchasing a monitor it is important to remember that CRTs of the same size have different size viewable areas and the bigger the viewable size area the better. Fair Trading Laws mean that television makers have been forced to clearly display the MVA on every machine, monitor makers are gradually also beginning to follow suit. 

3. Dot Pitch
This is a measure of the distance between two neighboring dots of the same color but located in different pixels (a pixel is made up of three dots one red, one blue and one green). It is measured from the center of one dot to another. 

4. Tube
CRTs can be divided into two different kinds, Conventional Tubes and Flat Square Tubes. The differences between the two can be discovered by viewing the picture from all angles. Previously, because it was impossible to make straight corners the picture tended to have a spherical protruding shape. Present monitors are called flat because the shape of the corners has been adjusted making the margins and corners appear straight and the picture flat. From the perspective of market distribution the conventional tube is a low-priced product, usually only found in 14 and 15 inch models. The flat square tube is used in all mid-priced and above monitors. If you require some special function monitors there is no need to emphasis the inclusion of a flat square tube as this is a fundamental of monitors with special functions. At present most of the special functions of CRTs can be separated into Dark-Tint, Aperture Grille, Croma Clear and Short Length. The dark-tint function makes the phosphor dots much darker so that the picture contrast is thus more distinct and the brightness is clear. There are a number of manufacturers using this technique because the increase to production costs is small but the improvement in picture quality is striking. 

Aperture Grille technology uses a phosphorous stripe instead of a dot. The mask consists of a number of equal sized, equally spaced slots, which allow more light to hit the phosphor coated screen creating a brighter picture and better color contrast. At the moment almost all monitors on the market using Aperture Grille technology CRTs are SONY Trinitron CRT and Mitsubishi Diamondtron CRT.

Although the sharpness and brightness of an Aperture Grille CRT are superior it does have some disadvantages. The Aperture Grille Mask has to be attached to the inside of the screen by a horizontal Damper Wire, this wire can be seen faintly by the user. Whether this line is seen or not is usually down to the peculiarities of an individual's eyesight. In a 15" model there is one wire at the top of the screen, whereas in a 17" model there are two wires, one at the bottom and one at the top of the screen.

Croma Clear is the brainchild of NEC, the technology is very similar to that of a traditional shadow mask, differing only in spot shape. The phosphor dots of the mask are elongated to make an oval shape resulting in better brightness and color.

The short Length CRT is the most recent technology on the market, with this technology the depth of the CRT is shortened but the screen size stays the same thus the monitor takes up less space on your desk. In fact a 17" short tube takes up less space on the desk than a traditional 14".

Screen resolution is measured in pixels, or picture elements. One pixel is the smallest area that can be manipulated by the computer. Resolution is always stated as the horizontal number of pixels by the vertical number of pixels. A screen displaying1600 x 1200 pixels has 1200 rows, each 1600 pixels wide. 

The requirement, that a monitor should be able to match all the different resolutions produced by the video card is fulfilled by most recent monitors. Monitors usually have two figures: Recommended Resolution and Maximum Resolution. The Recommended Resolution of a 15" monitor is 800 x 600 or 640 x 480; a 17" monitor is 1024 x 768 or 800x600 and a 19" monitor is 1280x1024 or 1024x768. 

To calculate the resolution we only need the figures for the Maximum Viewable Area, the ratio of the height and width of the Maximum Viewable Area and the CRT Dot Pitch. Using the example of a 17" Monitor with a Maximum Viewable Size of 16" and a height width ratio of 5 to 4 we can using algebra to calculate the width at 12.5"(317mm) and the height at 10" (254mm). As we already know the vertical dot pitch is 0.28 and the horizontal is 0.24 we immediately calculate a figure for the width of 317/0.24= 1320 and using the same method for the height. Using this method we can see that the optimal resolution is 1280x1024, if we expand to the maximum resolution of 1600x1200 the results are detrimental to the picture.