HP ZR30w Versus DoubleSight DS-309W, 30-Inch Monitors, 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 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.

In the gamma charts below, the yellow line represents 2.2, which is the most widely accepted standard for television, film, and computer graphics production. The closer the white measurement trace comes to 2.2, the better.

The HP’s gamma rides right around the 2.0 mark, which is a bit lower than the 2.2 standard. This results in an image with slightly less perceived contrast, especially in darker content where the gamma value is below 2.0. The tracking is reasonably flat, which is a plus. If HP added a gamma control, this issue could be fixed easily.

The DoubleSight also lacks a gamma selector. Let’s see how it turned out.

The DS-309W seems to be the opposite of the HP. The gamma is fine at the lowest signal levels and gradually rises to over 2.5 at the 90 percent point. This is a small error, and one that should be nearly invisible to the naked eye. Nevertheless, the DoubleSight’s tracking is not quite as good as the HP screen.

Here’s how our 30-inch panels compare to the 27-inch competition.

With a range of values spanning as high as 0.38, both monitors finish at the back in this metric. While their gamma tracking is fair, it isn’t quite as good as the other five screens.

By expressing the gamma error in percentage of deviation, rather than showing the absolute value, it’s a little easier to compare the performance of all the monitors.

With a low average value of 1.83, the HP ZR30w finishes last in gamma performance. The DoubleSight fares better because it sticks closer to the correct 2.2 standard. Its overall error is extremely small compared to the Auria and the HP.

ANSI Contrast Ratio

Another important measure of contrast is ANSI. To perform this test, a checkerboard pattern of sixteen zero 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, while factoring 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.

The HP’s ANSI number comes in a little lower than its on/off measurement. It is still quite high, however, at over 750 to 1. Only the 27-inch HP and the Asus QHD monitor from our last review do better in this test. The DoubleSight’s ANSI contrast is only a bit below its on/off number. This demonstrates consistent performance regardless of image content. In use, both panels look very good whether watching video, playing games, or working with productivity applications.