Monitor Black Level Test: Check Shadow Detail Online
Monitor Black Level Test. Click Start Black Level Test to run this monitor black level test and see how many near-black shades your screen shows. Use the monitor flicker test online to confirm whether your monitor shows this issue before you adjust settings or return it.
Interactive Tool
Use fullscreen mode in a dim room and let your eyes adjust for a couple of minutes. This sets the reading tip below.
The lowest patch number (1-32) you can separate from the black background. Enter 33 if you see none.
Every patch in the Full vs Limited RGB pattern is below RGB 16.
This monitor black level test steps your screen through a sequence of near-black shades so you can see exactly how many dark steps your panel actually separates before everything just looks like the same flat black. Click Start Black Level Test in a dim room, cycle through the shades with the arrow keys, and note where a shade stops looking distinguishable from pure black — that point is a rough read on your display's black-level performance.
Run this monitor black level test and in under a minute you'll know whether your screen shows the faintest shades above black or quietly swallows them. The pattern puts 32 near-black patches on a black background, and the number that stay distinguishable tells you how much shadow detail survives your current brightness, gamma and contrast ratio. It runs in any browser.
What the Monitor Black Level Test Measures
A monitor's black level is the light it still gives off when it receives a 0,0,0 signal. On an LCD the backlight stays on and the liquid crystal never blocks all of it, so pure black is really a faint glow; on an OLED the pixels switch off. A black level test asks how many steps above that floor you can actually see. Take a 280-nit IPS monitor with a contrast ratio of 1,100:1: its black luminance is 280 ÷ 1,100 ≈ 0.25 nits, and every patch has to rise visibly above it. The free monitor convergence test works on any screen — laptop, external monitor, or TV — with nothing to install.
Shadow Detail and Crushed Blacks
When the darkest steps merge into the background, the monitor is crushing them: values just above zero come out exactly like zero. You lose the texture in a dark gray coat, an enemy in a shadowed doorway in games, the night-sky gradient in movies and the deep tones of underexposed photos. The opposite fault flattens every image instead, because the near-black steps all look lifted.
Why the Darkest Steps Depend on Gamma
Patch luminance does not rise in a straight line with RGB values. With black \(L_b\), peak white \(L_w\) and display exponent \(G\), patch \(n\) emits:
$$L(n) = L_b + (L_w - L_b) \times \left(\frac{n}{255}\right)^{G}$$On the 280-nit example at \(G = 2.2\), RGB 2 adds just 2.6% to the 0.25 base, RGB 4 adds 11.8% (0.285) and RGB 8 reaches 0.392, or 54% above black. At \(G = 2.4\), RGB 4 adds only 5.1%, so the first patch you can pick out moves up a step or two although nothing is broken. That is why few monitors ever show RGB 1, and why the shadow levels you can see move whenever the tone curve does.
How to Run a Black-Level Test Correctly
A black-level test only works when nothing else lights the display and nothing in your monitor settings changes the picture while you look. Treat it as a quick visual check, not full calibration: the test pattern shows whether shadows are visible, not whether colours are accurate. Run the free monitor frame skipping test to check your display for this issue directly in your browser — no download required.
Set Up a Dark Room and Fullscreen Mode
Dim the lights, since ambient light falling on the panel raises the black you perceive. Give your eyes two minutes to adapt. Switch to fullscreen mode (F11 in most desktop browsers) so bright tabs don't pull your pupils closed; a full-screen pattern keeps the only light inside the patches. If your system applies a color profile, leave it on, because you want to test the picture you actually use.
Count the Gray Patches on the Black Background
Start at patch 32 and work down. The lowest number you can still separate from the background is your result. Then check the lowest patches you found: do neighbouring steps look different, or merely visible? The classic monitor black point check from photo workflows reveals one level at a time as an animated GIF; a static grid does the same job at a glance. On a CRT, brightness moved the black level directly; on an LCD it mostly moves the backlight.
Reading Your Crushed Blacks Test Result
Your result is the lowest patch number you can see at your usual brightness. Also check that the visible steps look neutral gray: a green or magenta color cast on the first few means the calibration needs work, not the brightness.
| Lowest patch you can see | What it means | Likely cause | What to do |
|---|---|---|---|
| 1-2 | Excellent shadow reproduction | Well-calibrated monitor in a dark room | Keep your current settings |
| 3-6 | Normal for most monitors | Black glow plus a 2.2-2.4 tone curve | Optional: raise brightness one step |
| 7-15 | Moderate crushing | Brightness too low or a shadow-darkening mode | Raise brightness, reset the picture mode |
| 16 or higher | Severe crushing | Full 0-255 signal sent to a monitor expecting limited 16-235 | Match the RGB range on GPU and monitor |
| All visible, background looks gray | Raised black | Brightness too high or a limited signal on a full-range monitor | Lower brightness, set Full RGB on both ends |
When the Lowest Steps Are Invisible
If nothing appears below about patch 16, the cause is almost always a range mismatch. Video-range signals code black as 16, so a monitor expecting them treats everything at or below 16 as black, and a full-range PC signal loses its first 16 steps. Invisible steps between 7 and 15 usually point to low brightness or a dark gaming preset; on a laptop, power-saving dimming is a common culprit. For photo editing and color management work, black crush like this means prints reveal shadow texture you never saw.
Gray Blacks and a Raised Black Floor
The reverse fault shows every patch, but the "black" background looks charcoal. Gray blacks appear when a limited signal (black = 16) reaches a full-range monitor, when brightness sits far above what the room needs, or when a shadow-boost mode lifts the floor. The picture looks washed out, dark grays lose depth and the grayscale bunches toward the middle.
A Streamer's Black Point Check on a VA Monitor
A viewer tells me the cave levels in my stream look like pure ink, so before I touch any OBS setting I check my own 32-inch monitor. The short answer: my lowest readable patch was 20, and after one menu change it was 4. That 16-step jump was the whole diagnosis.
What I know going in: a review measured this unit at 221.6 cd/m² white and 2,870:1, so its black sits at 221.6 ÷ 2,870 ≈ 0.077 cd/m². The PC feeds it over HDMI with the driver set to Full, and the monitor's HDMI black level option is on Auto. I turn the lamp off, go fullscreen, wait two minutes and count up from patch 1. Nothing until 20.
A reading of 16 or more points to a range mismatch, so I compute what patch 20 really becomes if the monitor is treating the signal as ITU-R BT.709 video levels (black at 16): (20 − 16) × 255 ÷ 219 ≈ code 4.7, which the formula puts at 0.110 cd/m², about 43% above black. Then I force the monitor's option from Auto to High and rerun:
| Setting | Lowest patch I can read | Computed lift above black |
|---|---|---|
| Driver Full, monitor Auto (acting as Low) | 20 | +43% |
| Driver Full, monitor High | 4 | +31% |
| Same, patch 3 (not readable) | 3 | +16% |
To cross-check, I recompute patch 4 by hand: 0.077 + 221.5 × (4/255)2.2 ≈ 0.101 cd/m². Both readings land at roughly 30-45% above black, which is my eye's threshold in this room. The hardware never changed; only the range did.
The non-obvious part: a result of 20 could also come from brightness set near zero, so the number alone doesn't prove a mismatch. What proves it is that changing only the range setting moved the answer by about 16 steps. If it had moved by one or two, I would be looking at brightness or the tone curve instead.
My judgement: the setting to watch is Auto. It guessed wrong here, and it can guess wrong again after a driver update or an input switch, so I now rerun this black level check after every GPU driver install. Next step is the same count at my late-night brightness, since that's when the cave levels get streamed.
How to Fix Problems Found by a Black Crush Test
Rerun the pattern after each fix below. A single change, usually the GPU range setting, often solves the whole problem.
Set Full RGB Range in the Graphics Driver
- NVIDIA: in the NVIDIA Control Panel, choose Display, then Change resolution, and set Output dynamic range to Full.
- AMD: in the graphics control panel's Display tab, set Pixel Format to RGB 4:4:4 PC Standard (Full).
- Intel: set Quantization Range to Full.
- Monitor or TV: set the HDMI black level option to High or Full when the PC sends 0-255, and to Low or Limited only for a 16-235 source.
Both ends must agree; a mismatch in either direction produces one of the two faults above.
Tune Brightness, Gamma and Black Equalizer
On an LCD, brightness drives the backlight, so raising it lifts black and white together. Raise it in small steps until the lost steps just reappear, then stop. Set gamma to 2.2 for everyday SDR use; 2.4 suits movie nights but hides an extra step or two. Gaming monitors add an OSD option such as Black eQualizer or Shadow Boost; keep it at default while testing, because it lifts shadows selectively and masks the real result. Contrast mostly affects highlights, so leave it near the factory value.
Disable Dynamic Contrast and Adaptive Brightness
Processing features move black from scene to scene, so a reading taken with them on tells you little. Choose a fixed picture mode such as Standard, sRGB or Custom, then switch off:
- Dynamic contrast and content-adaptive backlight control
- Adaptive brightness, ambient sensors and eco mode dimming
- Shadow-boost or esports "visibility" presets
Why Black Levels Shift With Brightness and Room Light
Your eyes judge black against everything around it: the brightest part of the image, the room light and whatever the surface reflects. Monitor black levels you checked at night can look different by day with identical settings, so a result only holds for the conditions you tested in.
The Brightness Setting at Night and in Daylight
At a low brightness setting an LCD leaks less light, so dark scenes look deeper, but go too low and the darkest steps vanish. At a high setting blacks drift toward gray. About 120 nits is a common desktop calibration target; set brightness so white pages feel comfortable, then rerun the pattern at your night and daytime levels.
Reflections, Coatings and Bias Light
Light bouncing off the surface adds to the black the monitor emits. Reflections from a window or lamp raise the perceived floor, and turning brightness up to fight them only flattens blacks further. A glossy coating looks inky at night but mirrors the room in daylight, while matte coatings diffuse glare at the cost of a faint haze. A dim bias light behind the monitor softens the jump between bright image and dim surroundings. Before you trust a result, kill any glare on the glass: one reflected lamp can hide the first three or four steps of the pattern.
Black-Level Pattern Results by Panel Type
The same black-level pattern reads differently on each display technology.
IPS Glow and Backlight Bleed on an LCD Screen
IPS monitors trade black depth for wide viewing angles. Typical native contrast is around 1,000:1, so the floor shows with the lights off, and IPS glow, a pale haze that shifts as you move your head, can wash over the corner patches. Backlight bleed stays fixed in one spot instead. VA monitors usually reach about three times the static ratio of an IPS model, so VA blacks hold up better, though their black uniformity deserves a look.
OLED and Mini-LED Monitor Blacks
OLED pixels switch off, so the background is effectively zero. Mini-LED backlights use local dimming: zones darken behind black areas, but a bright patch on a black field can cause blooming, a halo that lifts nearby steps. Under HDR, tone mapping changes how shadows render, so test SDR first and judge HDR separately; HDR gaming titles need their own in-game black slider.
Dithering in the Darkest Steps
If the first visible patches shimmer or crawl, the monitor uses temporal dithering (frame-rate control, or FRC), flickering subpixels between two neighbouring levels so the average lands on a shade it can't produce directly. A fixed checkerboard texture is static dithering. Both are common because a 6-bit driver offers only 64 levels per channel, and even an 8-bit one needs help placing 256 shades on the right curve in the shadows. Dithering only matters if the noise makes neighbouring steps impossible to tell apart.
Frequently Asked Questions
- What does a black level test show?
- It places near-black gray patches on a pure black background. The lowest patch you can still see tells you whether your monitor reproduces shadow detail or merges dark shades into black.
- Why can't I see the lowest patches?
- The darkest shades are being mapped to black. The usual causes are brightness set too low, a gamma that is too high, or a limited-range (16-235) signal clashing with a full-range setting.
- How do I get an accurate result?
- Dim the room, switch to fullscreen, give your eyes a couple of minutes to adapt and count from the darkest patch upward. Turn off dynamic contrast and adaptive brightness first.
- How do I fix crushed blacks?
- Set the GPU output range to Full (0-255) for a PC monitor, match the monitor's HDMI black level option, then raise brightness until the lowest patches just appear. On a TV, check its input range or HDMI black level setting.
- Does lowering brightness always give deeper blacks?
- No. Lower brightness reduces backlight glow on LCD monitors, but go too far and dark gray detail disappears. Aim for the lowest comfortable brightness that still shows the first few patches.
- Which panel type has the best black level?
- OLED gives true black because pixels switch off. Mini-LED gets close with local dimming but can bloom, VA usually beats IPS on native contrast, and IPS trades black depth for viewing angles.