Screen Brightness & Grayscale Test.
Step through a full-screen greyscale ramp from black to white to judge brightness, black level and greyscale banding — and check your panel is evenly lit. Free and in your browser.
How to judge brightness with a greyscale ramp
You can’t read nits from a web page, but a greyscale ramp is the classic way to judge brightness by eye. Eleven evenly-spaced steps from pure black to pure white tell you whether your black level, white level and midtones are set well — and whether the panel lights evenly.
- 1. Set the room and the panel. Turn off auto/adaptive brightness so levels don’t drift, and dim harsh room lighting so glare doesn’t wash out the dark steps.
- 2. Check the shadows. Step through 0 %, 10 % and 20 %. You should be able to tell each apart. If they’re one black blob, raise brightness; if 0 % already looks grey, you may have backlight bleed.
- 3. Check the highlights. Step through 80 %, 90 % and 100 %. If the top steps blend into one white, lower contrast until they separate.
- 4. Check uniformity. On the mid-grey (50 %) field, scan for patches that are brighter or darker — that’s uneven backlighting, most visible on large or budget panels.
Brightness, black level and bit depth
Why black is really dark grey
LCD/LED panels light black with an always-on backlight, so black is limited by the panel’s contrast ratio. OLED turns pixels fully off, so its black is far deeper. The gap between the 0 % and 10 % steps is a quick read on your contrast.
6-bit vs 8-bit vs 10-bit
More bits = more distinct levels and smoother ramps. Budget 6-bit (or 6-bit + FRC) panels can show visible steps where the ramp should blend. If your steps look chunky, the gradient test will confirm banding.
For accurate work — photo editing, HDR mastering — pair what you see here with a hardware colorimeter, which measures actual luminance in cd/m² and can calibrate the panel. This test is the fast, free first check that everything is roughly right.
What your results mean
Match what you see on the ramp below to the setting or issue it points at.
| What you see | What it means | What to do |
|---|---|---|
| All 11 steps look distinct, black is black, panel evenly lit | Brightness, contrast and black level are well set — a good panel | Nothing to do. |
| Several dark steps (0–20%) look identical | Black level or brightness is set too low, crushing shadow detail | Raise brightness; re-check the steps. |
| The 0% step looks grey rather than black | Raised black level or backlight bleed, common on TN/IPS more than VA/OLED | Run the uniformity test to check for edge bleed. |
| Bright steps (80–100%) blend into one white | Contrast is set too high, clipping highlight detail | Lower contrast until every step separates. |
| Hard edges between adjacent steps instead of a smooth change | Greyscale banding — likely a 6-bit panel or a low colour-depth setting | Confirm with the gradient test. |
| The mid-grey (50%) field has patches brighter or darker than the rest | Uneven backlighting across the panel | Check the uniformity test for a closer look. |
Frequently asked questions
How do I test my screen brightness?
Launch the test full screen and step through the greyscale ramp from black to white. On a good display every step looks distinct and evenly lit corner to corner. If several dark steps look identical, your black level or brightness is set too low; if the bright steps blend together, it is set too high. Adjust brightness/contrast until you can tell all eleven steps apart.
Can this measure my screen’s brightness in nits?
No. Nits (cd/m²) are a physical light measurement that only a hardware light meter or colorimeter can read — a web page has no access to it. This tool instead lets you judge brightness by eye: whether steps are distinct, whether black looks truly black, and whether the panel is evenly lit. For a real nits figure you need a measuring device or the manufacturer’s spec.
What is greyscale banding?
Banding is visible steps or bands where a smooth change from dark to light should be gradual. It shows up on cheaper 6-bit (or 6-bit + FRC) panels that can’t render all 256 grey levels smoothly. Watch the transitions between steps and the gradient test for hard edges instead of a smooth blend.
Why does black look grey on my screen?
On LCD/LED panels the backlight is always on, so "black" is really very dark grey — how dark depends on the panel’s contrast ratio and any backlight bleed. OLED screens switch pixels fully off, so their black is much deeper. Compare the 0 % and 10 % steps: if you can barely tell them apart, your contrast is good.
Does it work on a phone, tablet or TV?
Yes. It fills any screen with a browser. Tap or use the arrow keys to move between levels and Esc or the back button to exit. Turn off any auto-brightness / adaptive brightness first so the levels don’t shift while you test.