Our Monitor Picture Quality Tests

Vertical Viewing Angle

For the purposes of this article, we're going to compare two monitors: one with wide vertical viewing angles, the Acer Predator X27, and one with narrow vertical viewing angles, the BenQ EW3270U. No display is perfect, so you still may notice some change in color accuracy at very wide viewing angles with the Acer, but we don't expect most people to view the monitor this way. However, the loss in image accuracy is a lot more noticeable on the BenQ the moment you view it off-center.

Color washout happens when colors start losing their chroma and become less saturated. If you put a solid red image on a monitor and view it from different angles, it loses its chroma when it starts to appear almost pink, or light red, giving it a washed-out effect. To measure color washout, we use the colorimeter to measure pure red, green, and blue, and check to see at which angle they drop to 80% of their original chroma, or rather they lose 20% of their chroma. In the graphs below, the black horizontal line represents 80% of the original chroma, so we want to know at which angle it drops below that line.

The Acer surprisingly isn't that much better than the BenQ when it comes to color washout, so for the purposes of demonstrating good versus bad color washout, we've included the graph from the Dell S2721D instead. As you can see, the Dell retains its chroma for wide angles, except that red loses its chroma a bit faster when viewed from below. However, colors begin to look washed out on the BenQ at narrow vertical viewing angles.

Color washout - Dell S2721D

Color washout - BenQ EW3270U

We measure the color shift the same way we measure color washout, with a colorimeter reading pure red, green, and blue. However, color shift is related to the color's hue rather than chroma. A color's hue is how close it is to one of the six main colors: red, orange, yellow, green, blue, and purple. When a color shifts its hue, it either becomes closer to red or blue, depending on which end of the spectrum it's shifting towards. Hue can be defined in terms of degree, and we want to know at which angle the hue shifts by more than 3 degrees. In the graphs, the 3-degree shift is marked by the black horizontal lines, and when a color goes above or below these lines, it's considered a color shift.

The BenQ is actually incredible at maintaining its color hue at wide viewing angles, so in this case, we're going to show the Samsung Odyssey G5. As you can see, colors don't change their hue by more than 3 degrees on the Acer, but on the Samsung, red changes hue very quickly, followed by changes with blue.

Color shift - Acer Predator X27

Color shift - Samsung Odyssey G5

Brightness loss looks at the way a monitor loses its lightness at wide vertical viewing angles. It could be easy to confuse this with the monitor's actual brightness, but since that doesn't actually change as you view it off-center, what makes the screen appear dimmer is a change in lightness. With this test, we want to know at which angle the screen starts to look darker. We measure it using six slides: pure black, 20%, 40%, 60%, and 80% gray, as well as pure white. We test for their lightness at various angles; pure white has a lightness of 1.0 while 60% gray is 0.6, and pure black is 0.0. Any drop below 75% of their standard lightness is considered a brightness loss.

For the most part, the Acer maintains its lightness, and there's a noticeable drop only at very wide viewing angles. However, the BenQ quickly loses its lightness as soon as you move off-center, and darker colors actually appear lighter at wide angles, which also results in a gamma shift; we'll talk about that later.

Brightness loss - Acer Predator X27

Brightness loss - BenQ EW3270U

Black level raise is directly tied to the lightness of the monitor. As mentioned before, a perfect black level has a lightness of 0.0. This means that no light is coming from the backlight at all, but since LED displays can't achieve perfect blacks, their black level value is above 0.0. So what we want to look for when measuring the black level raise is how much the pure black slide in the brightness loss test doubles its original lightness. This is the angle where blacks start to look more gray. Between the Acer and the BenQ, it's actually the Acer whose black level raises quicker, so blacks start to look different at about 24 degrees above center, while the BenQ maintains its black level 46 degrees above center.

Gamma shift is another test that's tied to the brightness loss test. Gamma defines the brightness and darkness of shades of gray. If the gamma is too high, scenes appear too dark, and you start to lose details in shadows. If it's too low, scenes are too bright, and it may seem like those shadows aren't there at all. Using the 20%, 40%, 60%, and 80% gray slides in the brightness loss test, we want to know at which angle their original gamma starts to change. If you look at the brightness loss graphs, you'll see there are dotted lines, and these represent the ideal gray value relative to pure black and pure white. If the lightness level of these grays deviate from the dotted lines, that means the gamma is shifting. In the case of the Acer and BenQ with the lightness graphs above, only dark grays begin to change gamma at very wide viewing angles on the Acer, and it's hardly noticeable. However, gamma shift happens very quickly on the BenQ, and even at wide angles the 20% gray slide starts to look like 60% gray.