Our Monitor Picture Quality Tests

Horizontal Viewing Angle

Throughout this article, we're going to compare monitors: the Dell S2721DGF, which has wide viewing angles, and the LG 32GK850-B, which has narrow viewing angles. As you can see, the image remains accurate when viewing off-center on the Dell. No display has perfect viewing angles, so you still notice some color shift at very wide angles, but most people aren't looking at monitors from the side like that. On the other hand, the image on the LG starts to look different as you move off-center, and the decrease in image quality happens more quickly.

Color washout is when colors start to lose their chroma, or when they lose their saturation. If you're looking at a standard blue color, it loses its chroma when it starts to look blue/gray and it's not the same color anymore. To test for color washout, we measure pure red, blue, and green, and we measure the angle at which each color drops to 80% of its original chroma. These graphs aren't very difficult to read; the x-axis represents the viewing angle and the y-axis represents the color's chroma.

As you can see, colors retain their chroma at wide angles on the Dell, while the colors lose their chroma very quickly on the LG.

Color washout - Dell S2721DGF

Color washout - LG 32GK850G-B

Color shift is similar to color washout, except we're looking at the change in a color's hue. The hue defines how close a color is to one of the six main colors: red, orange, yellow, green, blue, and purple. A shift in hue changes the color and makes it either appear more red or blue, depending on which end of the color spectrum it's changing to. Once again, we measure red, green, and blue, and test to see at which viewing angle the hue changes by more than 3 degrees. In the graphs below, the acceptable hue shift range is marked by the horizontal black lines. If a color increases or decreases past these lines, it's considered a color shift.

These graphs are a bit more difficult to read than color washout, but you can see how green and blue retain their hue for a wide angle with the Dell; only red starts to change sooner. The LG is actually outstanding at retaining the color hue, so instead, we've shown the graph for the MSI Optix G27C4, which isn't as good. You can see that all three colors, especially red, start to lose their hue a lot sooner.

Color shift - Dell S2721DGF

Color shift - MSI Optix G27C4

In this test, we don't measure if the monitor loses brightness and becomes dim, but rather we measure how much it loses its lightness. In other words, at which angle does the image start to appear darker? We measure the lightness using six test slides: pure black, 20% gray, 40% gray, 60% gray, 80% gray, and pure white, and we measure each slide at various angles. The pure white slide has a lightness measure of 1.0, while pure black is 0.0, and we want to see when the lightness of any of the slides drops to 75% of its original value.

As you can see, the image retains its brightness at wider angles on the Dell than the LG. Pure white drops to 75% of its original lightness at about 50 degrees on the Dell and less than 30 degrees on the LG. Also, pure black actually becomes lighter on the LG at very wide angles, meaning it's not pure black anymore.

Brightness loss - Dell S2721DGF

Brightness loss - LG 32GK850G-B

Black level defines how bright the screen is when displaying its darkest dark. A monitor that can display deep blacks has a low black level because it's not emitting much light. However, monitors with low contrast have blacks that appear gray, meaning there's still some light coming out. The black level raise measures when the black level doubles its lightness, causing blacks to appear gray. In the case of the Dell, the black level raise is measured at 70 degrees, meaning the blacks look the same at wide angles. However, the LG has a black level raise of 18 degrees, so blacks look closer to gray than pure black when viewed from the side.

Gamma defines the brightness of shades of gray. Having a monitor with a proper gamma is important for scenes or games with shadows. If gamma is too high, the image appears too dark and you lose some details in the shadows. If gamma is too low, the image is too bright. Using the same grayscale slides from the brightness loss test, we want to see at which angle do those grays shift by 3% from their relative position between pure black and pure white. Essentially, we test for which angle the grays start to change. Looking at the graphs above in brightness loss, you'll notice there are dotted lines, and these represent the ideal gray value relative to pure white and pure black. If the grays start to deviate from the dotted lines, it means gamma is shifting. As you can see, the Dell maintains gamma stable for wide viewing angles, while the LG starts to shift at narrow viewing angles.