If the sides bow outward, it is often called barrel distortion. 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. Spacing between groups of red, green, and blue phosphor dots on the screen.
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.