Results: Viewing Angles And Uniformity
The more monitors we test, the more we can see that off-axis viewing performance is dependent not only on pixel structure (IPS, PLS, TN, etc.), but the backlight technology as well. And we can see that the anti-glare layer makes a difference too.
Off-axis image quality remains the weak point of TN screens. In our composite photo, you can see an obvious color shift towards red in the horizontal pictures. Even in the head-on shot, there is a slight tint due to the wide-angle lens on our camera. The vertical images don’t show any color issues, but detail in the 11-step grayscale pattern is almost non-existent. It’s very difficult to distinguish the brightness levels from one another.
Since gamers typically sit close to their monitors, 27 inches really does seem to be the practical size limit for a TN panel. If it were any larger, you’d see color tint and detail loss in the sides of your display, even from dead center.
Screen Uniformity: Luminance
To measure screen uniformity, zero and 100-percent full-field patterns are used, and nine points are sampled. First, we establish a baseline measurement at the center of each screen. Then the surrounding eight points are measured. Their values are expressed as a percentage of the baseline, either above or below. This number gets averaged. It is important to remember that we only test the review sample each vendor sends us. Other examples of the same monitor can measure differently.
First up is black field uniformity.
We haven’t tested many TN screens, but the two in this group acquit themselves very well. BenQ’s result is the lowest we’ve recorded to date. There’s certainly no uniformity compensation look-up table needed here!
Next is the white field measurement.
The white field result is right about average for the displays we’ve measured. In the XL2720Z’s case, the center of the screen is slightly hotter than the surrounding zones. It’s extremely hard to see with the naked eye, though. If you could reduce that hotspot to equal the rest, the result would be closer to three percent.
Screen Uniformity: Color
To measure color uniformity, we display an 80-percent white field and measure the Delta E error of the same nine points on the screen. Then we simply subtract the lowest value from the highest to arrive at the result. A smaller number means a display is more uniform. Any value below three means a variation that is invisible to the naked eye.
The XL2720Z has excellent grayscale tracking, and that performance holds up at all points on the screen. There is no visible color tint anywhere, just a smooth white tone at all brightness levels.
