Why Do Blacks Look Grey? Full vs Limited RGB Range

You connect a new monitor over HDMI and the picture looks flat: blacks are dark grey, whites are dull, everything looks faded. Or the opposite happens — shadows turn into solid black and bright skies lose their detail. Before you blame the panel, check one setting that catches out a huge number of people: the RGB range.

Two ways to count from black to white

Digital video stores each color channel as a number. In 8-bit color there are 256 steps, from 0 to 255, but there are two conventions for using them:

• Full range (0–255): 0 is black and 255 is white. This is what computers use.
• Limited range (16–235): black sits at 16 and white at 235. It comes from broadcast video and is still the standard for TVs, Blu-ray and streaming.

Neither is better. The problem only appears when the source and the screen disagree.

What a mismatch looks like

• The source sends limited, the screen expects full. Black arrives as 16, which a full-range screen shows as dark grey, and white arrives as 235, which it shows as slightly dim. The result is the classic washed-out, low-contrast look.
• The source sends full, the screen expects limited. Everything from 0 to 16 is shown as the same black, and everything from 235 to 255 as the same white. Shadow detail disappears and highlights clip. The picture looks punchy but loses detail at both ends.

Why it happens over HDMI

HDMI carries both computer and TV signals, so graphics cards and displays try to guess which one you want. Many graphics drivers switch to limited range automatically when a screen reports a TV-style resolution such as 1920×1080 at 60Hz — even when it's a computer monitor. DisplayPort and USB-C connections are almost always full range, which is why the same monitor can look different from one input to the next.

How to test for it

The Black Level Test shows a row of near-black steps starting at 0, and it makes both mismatches easy to spot:

• Every step looks like the same black up to about 16, and the steps above are distinct: shadows are being crushed — the source is sending full range to a screen that expects limited.
• Even the 0 step is visibly grey, and nothing is truly black: the source is sending limited range to a full-range screen. Compare it with a full-screen Black Screen in a dark room; on a mismatched setup neither looks properly black.

The bright end is easier to see with the Greyscale Test: if the last few steps of the stepped ramp merge into one white, highlights are clipping. The Contrast Test makes a good overall sanity check after you change a setting.

Bear in mind that a budget panel can show grey blacks and faint steps for other reasons. The giveaway for a range problem is that changing a single setting makes a dramatic difference.

How to fix it

The rule is simple: both ends must match. For a computer, full range on both ends is best.

On the computer

• NVIDIA: in the NVIDIA Control Panel, open Change resolution, choose to use NVIDIA color settings, and set Output dynamic range to Full.
• AMD: in AMD Software's display settings, set Pixel Format to the RGB 4:4:4 option marked Full RGB.
• Intel: in the Intel Graphics Command Center's display settings, set Quantization Range to Full.
• Mac: macOS doesn't offer a simple range switch for external displays. If a monitor looks washed out over HDMI, try a USB-C or DisplayPort connection, and set the monitor's own range option to match.

Menu names move around between driver versions, so look for the nearest equivalent if yours is different.

On the display

Look in the picture settings for RGB range, HDMI black level or simply black level. The options are usually Auto, Full (sometimes called High or Normal) and Limited (sometimes called Low). If Auto gets it wrong, set it by hand to match the source.

Consoles and streaming boxes

Games consoles and streaming devices have their own range setting, usually left on Automatic. Leave it there unless you see one of the symptoms above — and if you do change it, change the TV to match.

What it isn't

If blacks still look grey in a dark room after the range is right, you're seeing the panel's native black level: every LCD leaks some light, and IPS panels especially. Contrast Ratio Explained covers what to expect from each panel type, and Gamma Explained covers shadows that look wrong for a different reason. HDR adds its own tone mapping on top — HDR Explained is the place to start if the problem only appears in HDR mode.