Results: Brightness And Contrast
Before calibrating any panel, we measure zero and 100-percent signals at both ends of the brightness control range. This shows us how contrast is affected at the extremes of a monitor's luminance capability. We do not increase the contrast control past its clipping point. While that would effectively increase a monitor’s light output, the brightest signal levels would not be visible, resulting in crushed highlight detail. Our numbers show the maximum light level possible with no clipping of the signal.
The comparison group consists of wide-gamut professional-quality monitors. We have Dell’s two 4K screens, the UP2414Q and UP3214Q. Also included are the high-end NEC PA272W and ViewSonic VP2772 QHD displays. Finally, we threw in Samsung’s S27B971D. It’s an sRGB-native monitor, but it comes with a factory calibration and is one of the most accurate screens we’ve ever measured.
The PG2401PT ships set to Standard mode, but we changed it to Adobe RGB to reflect its native gamut. Our initial reading was 174.5498 cd/m2, a good deal less than BenQ’s spec of 350 cd/m2. A little digging through the OSD revealed that the uniformity compensation was turned on, though. Switching it off gave us the 313.2685 cd/m2 value you see above. It seems that uni-comp reduces brightness by a significant amount.
Uni-comp doesn’t affect black level as severely. You’ll see later that zero brightness results are pretty much the same whether it’s on or off. But a .4031 cd/m2 reading is fairly high for our minimum black level test.
Maximum contrast is a little disappointing at only 777.1 to 1. Granted, that's enough to beat Samsung and one of the Dells, but NEC sets the bar high with its 1038.7 to 1 ratio.
We believe 50 cd/m2 is a practical minimum standard for screen brightness. Any lower and you risk eyestrain and fatigue. Most pro-grade monitors bottom out well below that. However, the PG2401PT is an exception, measuring 107.3534 at its minimum brightness setting. We believe that’s a little high, since many pros like to calibrate at 80 cd/m2. Of course, you can reduce that number by turning on the uniformity compensation. Then the minimum number is around 60 cd/m2.
Uniformity compensation is still off in this test. Turning it on raises the black level ever so slightly. Either way, the result is merely fair.
Minimum contrast stays pretty consistent at 783.1 to 1. The PG2401PT finishes in second place mainly because its minimum brightness is higher than the others. We’ll show you the impact of uniformity compensation on contrast below.
Since we consider 200 cd/m2 to be an ideal point for peak output, we calibrate all of our test monitors to that value. In a room with some ambient light (like an office), this brightness level provides a sharp, punchy image with maximum detail and minimum eye fatigue. On many monitors, it’s also the sweet spot for gamma and grayscale tracking, which we'll look at on the next page. Many professionals prefer a 120 cd/m2 calibration in darker rooms. We find that makes little to no difference on the calibrated black level and contrast measurements.
Normally we don’t show the calibrated white level chart because the monitors we test are within a hair of 200 cd/m2. In the PG2401PT’s case, we want to illustrate the difference that results when uniformity compensation is turned on. The reduction in brightness is almost 44 percent.
We’ve reviewed several displays with uni-comp and in every other case, the black level went up noticeably when we turned it on. BenQ's PG2401PT is an exception. Here, the difference is almost negligible.
Unfortunately, the reduction in white level means contrast drops the same 44 percent with uni-comp on. Now you have to make a decision: is the feature worth using? We'll answer that question definitively in a couple of pages.
ANSI Contrast Ratio
Another important measure of contrast is ANSI. To perform this test, a checkerboard pattern of sixteen zero and 100-percent squares is measured. We get a somewhat more real-world metric than on/off measurements because we're testing the display’s ability to simultaneously maintain both low black and full white levels, plus 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 ANSI numbers stay fairly close to the on/off results, which is an indicator of excellent build quality. The PG2401PT appears to have a deep grid polarizer that enhances image clarity and minimizes light bleed between pixels. Interestingly, uniformity compensation actually raises the ANSI result a little.