MonsterVision LCDs

Lab Notes: The Angle on LCD Monitors

You see an LCD's brightest light and truest colors only when you are positioned directly in front of it. Brightness, and therefore contrast, falls off and colors change as you move to the side (horizontally) or up and down (vertically)--eventually reaching a point where you can no longer discern the image. Low-cost LCDs extend the viewing range by using a diffusion film on the glass to spread the light over a wider angle. More-expensive technologies, such as in-plane switching and multidomain vertical alignment, change the arrangement of liquid crystals to increase viewing angle.

Monitor vendors employ sophisticated equipment to measure angle of view. They do not use identical methods, however, so numbers from assorted companies may not be comparable. To roughly gauge how the LCDs in this review compare to each other, the PC World Test Center devised a simple test with help from Raymond Soneira of DisplayMate Technologies. You can download DisplayMate's monitor-testing software, select "Gray-scale Linearity Check," and test your monitor yourself.

The test takes advantage of a simple fact about LCDs: Bright pixels vary much more with viewing angle than dark pixels do. DisplayMate illustrates this with a screen showing two gray rectangles: a "dithered" one, consisting of alternate fully white and black pixels, and another that is uniformly gray. The difference in brightness is easy to see when you view the monitor head-on. As you move to the side, the difference tapers off until, eventually, the two rectangles appear identical. To calculate the angle of view, we placed each monitor on a turntable and rotated it until the two rectangles reached the "no difference" point.

Because we use this measurement method, our viewing angle numbers are not directly comparable to those that monitor vendors publish. However, the dissimilarities among products in our measurements (the angles ranged from 108 to 167 degrees) do illustrate how viewing angle varies for the monitors in this review, despite their all having the same vendor-specified horizontal viewing angle of 170 degrees.

Horizontal angle of view measures the full sweep from left to right.