X-bit labs

Xbit Labs Presents: LCD Monitors Testing Methodology Indepth (page 8)

Category: Other

by Oleg Artamonov

[ 06/10/2007 | 10:28 PM ]

Brightness and Contrast Ratio

The monitor’s brightness and contrast ratio are measured with a ColorVision Spyder calibrator at three combinations of settings: 1) maximum brightness and contrast, 2) factory settings, and 3) a 100nit level of white. The last combination is not something recommended, yet we specify at which settings it is achieved. It serves as a common reference point so that we could compare different monitors and check out how the monitor’s parameters change in comparison with the factory settings which usually produce a twice higher level of white. For practical purposes, the brightness of 100 nits corresponds to typical settings for working with text in a well-lit office room.

The calibrator measures the levels of black and white. The latter is what is referred to as the monitor’s brightness. The ratio of the two is the monitor’s contrast ratio. The results are listed in a table:

As for specific numbers, you need a brightness range of 80-150nits for home use. All modern monitors cover this range easily. A brightness of 200 nits and higher may be necessary if you play games or watch movies in a brightly lit room, up to direct sunlight.

As opposed to brightness, you can’t have too much of contrast ratio. The higher it is, the blacker the monitor’s black seems, which is especially conspicuous when you are watching a movie in semidarkness. Moreover, a high contrast ratio partially conceals any irregularities in the backlight. In our tests, a contrast ratio of 200:1 is acceptable. 400:1 and higher is good.

We want to note that you should not compare the results of our measurements (using a calibrator) with the specified numbers. The calibrator is not actually meant for measuring contrast, so its error can be quite high. However, our results are quite sufficient for a comparative test.

And finally, the dynamic contrast technology has become popular recently. When it is enabled, the monitor is adjusting the backlight brightness depending on the current image, reducing that brightness for dark images and vice versa. The ordinary contrast ratio is the ratio of white to black at the same backlight intensity, while the dynamic contrast is calculated as the ratio of white at the maximum backlight intensity to black at the minimum backlight intensity. In other words, it equals the ordinary contrast ratio multiplied by the backlight adjustment range. We measure only static contrast in our tests but some manufacturers declare only dynamic contrast for their newer models – so don’t be surprised when you see TN-based monitors with a specified contrast ratio of 2000:1 and even higher.