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GeChic On-Lap 2501M 15.6" Battery-Powered Monitor, Tested

Results: Gamma And ANSI Contrast Ratio


Gamma is the measurement of luminance levels at every step in the brightness range from 0 to 100 percent. This is important because a poor gamma can either crush detail at various points, or wash it out, making the entire picture appear flat and dull. Correct gamma produces a more three-dimensional image, with greater depth and pop. Meanwhile, incorrect gamma can negatively affect image quality even in monitors with high contrast ratios.

We’re now including the gamma tracking charts for all the monitors we test. The yellow line represents 2.2. The closer the white measurement trace comes to 2.2, the better.

The On-Lap does fairly well in this test. The values drop slightly as the signal level approaches 90 percent. A lower gamma value means the image is too bright at that luminance point. The measurement at 90 percent is around 1.8, which equates to four percent too high.

Turning to the comparison charts, the On-Lap performs adequately versus its competition. We don’t have gamma data for any of the TN-based panels from past reviews, so we only included the IPS monitors in these charts.

Bear in mind that the four IPS panels in this comparison boast superb gamma performance, and the On-Lap is only slightly behind the group.

The gamma value range tells us how close each signal level from zero to 100 percent comes to the 2.2 standard.

This is a very good result. The lower numbers indicate flatter gamma tracking. This means the display will closely match the mastering specification of the original content, so you’ll see maximum detail no matter what the brightness level is set to.

ANSI Contrast Ratio

Another important measure of contrast is ANSI. This is a relatively new benchmark for our monitor reviews. To perform this test, a checkerboard pattern of sixteen 0 and 100 percent squares are measured. This is somewhat more real-world than on/off measurements because it tests a display’s ability to simultaneously maintain both low black and full white levels. This test also factors in screen uniformity. The average of the eight full-white measurements is divided by the average of the eight full-black measurements to arrive at the ANSI result.

It’s not surprising that the On-Lap doesn’t do particularly well. After all, the on/off contrast is only fair. On the plus side, its ANSI contrast ratio is slightly higher than its on/off ratio, meaning that contrast will be maintained no matter what image is being displayed.

Christian Eberle
Christian Eberle is a Contributing Editor for Tom's Hardware US. He's a veteran reviewer of A/V equipment, specializing in monitors.