Poor convergence can produce a fuzzy look similar to what a color picture in a newspaper looks like when the registration is off. Convergence is measured in milimeters taken from two locations on the screen. Zone A represents a circle in the center of the screen, and Zone B represents the outer half of the screen. It is significantly more difficult to keep a sharp picture at the edges. That's why some manufacturers reduce the default viewable area by placing a black border around the edges of the screen in order to achieve a sharper image.
Sharpness increases productivity.
Attempting to read Fuzzy characters will significantly reduce reading speed. Slower reading speed will decrease productivity. Since most business applications use a white background with black text, pure white and crisp black becomes important to help the eye make the transition from the background to the text. Unfortunately most manufacturers consider their convergence specification to be confidential, which makes comparisons difficult. If the monitor manufacturer doesn't publish their convergence specifications, you can use a monitor testing utility such as DisplayMate to create a grid pattern of thin white lines on a black background.