Monitor Jargon

21" Monitors Reviewed

Image-quality terms
Convergence Relates to the monitor's ability to match the red, green, and blue colors to form white. If the colors don't line up correctly, a white image has a tinge of color on one side or another. Convergence is most difficult to adjust in the corners of the screen.

Focus Ability of a monitor to display crisp pictures. More advanced monitors have dynamic beam focus, where the focus of the screen is fine-tuned from area to area rather than approximated for the entire surface.

Geometric distortion General term used in our table to describe problems with linearity, pincushion, and trapezoid distortions.

Pincushion Distortion seen when the sides of the screen bow inward. If the sides bow outward, it is often called barrel distortion.

Purity Exactly what it implies—color purity. Bad purity often manifests itself as muddiness in one area of the screen. It can result when the CRT's frame becomes magnetized. The degauss button fixes this. Trapezoid Distortion seen when the image's width is different at the top and bottom of the screen (assuming, of course, you start with a rectangular image).

Specification terms
Dot pitch Spacing between groups of red, green, and blue phosphor dots on the screen. Also specified as the spacing of the holes in the shadow mask (which is internal to the CRT and can't be seen from the outside). Some manufacturers specify aperture-grille spacing instead of dot pitch.

Resolution Screen resolution is measured in pixels, or picture elements. One pixel is the smallest area that the computer can manipulate. Resolution is stated as the horizontal number of pixels by the vertical number of pixels. A screen displaying 1600X1200 pixels has 1200 rows, each 1600 pixels wide.

Vertical scan rate or refresh rate Number of times the screen is redrawn per second. Minimum acceptable refresh rate is 70Hz. The higher the refresh, the better the image.

Other
Aperture grille An aperture grille uses vertical wires to direct electron beams to phosphors of a certain color.

Flat-square tube A cathode-ray tube (CRT), or picture tube, that has a face plate that is flatter and squarer than that of a standard tube, but is still neither totally flat nor totally square.

Shadow mask A metal screen located just inside the CRT that prevents electron beams from striking incorrect color phosphors.