BLACK LEVEL TESTER
Advanced display calibration — test near-black shadow detail, backlight bleed, OLED ABL, gamma accuracy, uniformity and more. Use fullscreen for accurate results.
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DISPLAY SCORE
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BLACK LEVEL BENCHMARK
Full Suite · 9 Tests · Shadow / Bleed / OLED / Gamma / Uniformity
FULL SUITE
TEST MODE
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ELAPSED
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STEPS SEEN
Unknown
PANEL TYPE
NEAR-BLACK GRADIENT
Steps visible 0–32
SHADOW DETAIL—
/ 16 STEPS
BLACK CRUSH TEST
0–16 distinct values
CRUSH DETECT—
/ 16 VISIBLE
BACKLIGHT BLEED
IPS glow / edge bleed
BLEED—
USER RATING
GAMMA NEAR-BLACK
Target: γ 2.2
GAMMA—
γ ACCURACY
ANSI CHECKERBOARD
Local contrast ratio
CONTRAST—
SCORE / 100
COLOR BLACK BIAS
R/G/B tint near black
COLOR—
NEUTRAL %
PANEL UNIFORMITY
9-zone dark analysis
UNIFORMITY—
UNIFORMITY %
OLED ABL TEST
Auto brightness limiting
OLED—
USER RATING
SHADOW DETAIL
Dark scene visibility
DETAIL—
VISIBILITY %
NEAR-BLACK GRADIENT
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RATE WHAT YOU SEE
STEP COUNTER — HOW MANY STEPS CAN YOU SEE?
RESULTS
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FINAL SCORE
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STEPS VISIBLE
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CRUSH LEVELS
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GAMMA ACC.
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BLEED RATING
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UNIFORMITY
RESULT BADGE
Run the full suite to receive your display score
DISPLAY ASSESSMENT
Run the full suite to receive a detailed display assessment.
LUMINANCE HISTOGRAM
REFERENCE
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| PANEL TYPE | BLACK LEVEL | NEAR-BLACK STEPS | BLEED | UNIFORMITY | ABL |
|---|---|---|---|---|---|
| IPS / Nano-IPS | 0.15–0.40 nit | ≥ 12 / 16 | IPS glow (corners) | 85–92% | None |
| VA | 0.02–0.10 nit | ≥ 14 / 16 | Low | 78–88% | None |
| TN | 0.20–0.60 nit | 8–12 / 16 | Low–Moderate | 70–82% | None |
| OLED / AMOLED | 0.000 nit (true) | 16 / 16 | None | 95–99% | Yes (power) |
| Mini-LED | 0.005–0.05 nit | ≥ 13 / 16 | Zone limited | 88–96% | None |
CONFIG
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PANEL TYPE HINT
GAMMA TARGET
TOGGLES
ANIMATE GRADIENT
Slow colour animation on near-black gradient
SHOW PIXEL LUMINANCE
Enable hover pixel sampler on canvas
OLED OPTIMISED PATTERNS
Reduce static white elements for OLED
SOUND ON COMPLETE
Beep when test suite finishes
ACCENT COLOUR
COMPLETE GUIDE
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GET ACCURATE RESULTS IN 4 STEPS
Follow this setup before running any test for reliable, comparable results.
01
DARKEN THE ROOM
Dim or turn off room lights. Ambient light reflecting off your screen adds perceived light to black areas, making poor black levels invisible. A dark room is the single biggest accuracy factor.
PRO TIP Wait 2–3 minutes for your eyes to adapt to the dark.
02
WARM UP YOUR DISPLAY
Let your monitor run for at least 20–30 minutes before testing. Cold LCD panels can show slightly different black levels and colour accuracy compared to their warmed-up state.
PRO TIP OLED panels need less warm-up — 5 minutes is sufficient.
03
SET NORMAL BRIGHTNESS
Set your display brightness to your typical usage level — not max. Testing at max brightness makes IPS glow and backlight bleed worse and makes near-black easier to see artificially.
PRO TIP 120–160 cd/m² is a good reference brightness for SDR testing.
04
USE FULLSCREEN MODE
Browser UI, Windows taskbar, and page background colours all affect your perception of test patterns. Press the FULLSCREEN button or hit F for any pattern to test in a true full-black environment.
PRO TIP Press ← → arrow keys to cycle patterns in fullscreen.
RECOMMENDED TEST WORKFLOW
Select your panel type
Open Settings → Panel Type Hint and choose your panel (IPS, VA, OLED, TN). This calibrates scoring thresholds to realistic expectations for your display technology.
Run Full Suite or a targeted mode
Press RUN TEST for automatic sequencing through all 9 tests, or pick a mode from the category bar (e.g. SHADOW DETAIL or BLEED CHECK) to focus on a specific issue.
Use fullscreen for visual tests
For Near-Black Gradient, Black Crush, and Full Black tests the tool will show each pattern — click the fullscreen button then report how many steps you can see using the step counter buttons.
Rate subjective tests with stars
For Backlight Bleed and OLED ABL tests, use the star rating widget. Look at the pattern carefully, rate what you observe (1 = very bad, 5 = excellent), then press Apply Rating.
Review your score & assessment
Check Summary Statistics for your overall score (0–100), grade, and the auto-generated display assessment with specific recommendations for your panel.
NEAR-BLACK GRADIENT
SHADOW DETAIL
Target: ≥ 14 / 16 steps
A continuous gradient from absolute black (0,0,0) to near-white (32,32,32). The top strip covers 0–32 in 1-step increments; the bottom strip shows 0–16 in fine detail. Count how many distinct steps you can see from the left edge — the number directly reflects your display's shadow detail capability.
WHAT TO LOOK FOR
- Excellent (14–16 visible): Very good shadow gradation, well-calibrated black point
- Average (10–13 visible): Typical for IPS — acceptable for most content
- Poor (< 10 visible): Black crush present — dark scenes lose detail
💡 If the first 2–3 bands all look identical, your display has black crush. Lower the "Black Level" or "Shadow" in OSD settings.
BLACK CRUSH STEPS
CRUSH DETECT
Target: All 17 levels distinct
17 horizontal bars from rgb(0,0,0) to rgb(16,16,16), each clearly labelled. Unlike the gradient, these are discrete steps with clean borders. This makes it easy to see exactly where your display "crushes" adjacent levels into the same visual output.
WHAT TO LOOK FOR
- No crush: Each bar has a visibly different brightness — a thin gap between levels
- Mild crush: Levels 0–2 look the same, 3+ are distinct — minor calibration offset
- Severe crush: More than 4 levels are identical — display black level is too high in OSD
💡 Fix: In your monitor OSD, lower "Black Level", "Shadow Boost", or switch off any "Dark Stabilizer" feature which clips low values.
FULL BLACK
BLEED
Best viewed: Fully dark room
Pure #000000 across the entire canvas. Use fullscreen. This is the definitive test for backlight bleed (LCD) and IPS glow. After going fullscreen, let your eyes adjust for 30 seconds before judging.
WHAT TO LOOK FOR
- True black everywhere: OLED / good VA panel — excellent result
- Corner glow: IPS glow — a wide, soft-edged brightening in corners — normal for IPS
- Bright spots or streaks: Backlight bleed — hardware defect, especially bad near edges
💡 IPS glow shifts position when you move your head — backlight bleed does not. Use this distinction to tell them apart.
ANSI CHECKERBOARD
CONTRAST
Target: Sharp hard edges
Alternating pure black (#000) and pure white (#FFF) squares in an 8×5 grid. Used to measure local / ANSI contrast ratio — the contrast between adjacent black and white squares on the same screen area, which is lower than the full-screen contrast ratio.
WHAT TO LOOK FOR
- Hard, crisp edges between squares — high local contrast
- Slight halo or glow around white squares onto black — mild local dimming artifact (Mini-LED)
- Black squares look grey or washed-out — low ANSI contrast
💡 Mini-LED displays may show "halo" around white squares due to zone-limited local dimming — this is a technology trade-off, not a defect.
SHADOW DETAIL SCENE
DETAIL
Target: Count all 16 rings
A set of concentric circles from absolute black at the centre outward to rgb(32,32,32) at the edge. This simulates a real-world dark scene (e.g. night sky, cave, cinematic film-noir shot). Count how many distinct rings you can see.
WHAT TO LOOK FOR
- Can see all 16 rings clearly: Excellent shadow detail for real content
- Inner 3–4 rings invisible: Normal for TN / lower-end IPS — dark scenes may feel flat
- Fewer than 8 rings visible: Poor shadow detail — significant near-black information lost
OLED ABL TEST
OLED
LCD = No change expected
A large white rectangle (~25% APL) on a black background. On OLED panels, the Auto Brightness Limiter (ABL / ASBL) may reduce peak brightness as large white areas would draw too much power. Watch if the white patch dims over 5–10 seconds.
WHAT TO LOOK FOR
- LCD / TN / IPS: Brightness stays constant — expected and correct
- OLED slight dim: Mild ABL — normal operation to protect the panel
- OLED significant dim: Aggressive ABL — brightness may visibly drop during bright video scenes
💡 ABL is not a defect — it is a power and longevity management feature. Some OLED TVs let you reduce it in settings under "OLED Pixel Brightness".
COLOR BLACK BIAS
COLOR
Target: Neutral gray strips
Four vertical gradient strips: pure Red, Green, Blue, and Neutral Gray near-black (all starting at 0). Compare the neutral gray strip to the others. If the "neutral" strip appears to have a colour cast at low values — bluish, greenish, or reddish — your display has a colour tint bias in the black region.
WHAT TO LOOK FOR
- Neutral strip looks exactly grey — no tint bias, excellent white balance
- Slight blue/warm cast — common, correctable via OSD colour temperature
- Strong green or magenta tint — significant colour calibration issue
💡 Use the Pixel Sampler (click the canvas) to read exact RGB values from the neutral strip to detect tiny tint biases invisible to the naked eye.
GAMMA STEPS
GAMMA
Target: γ 2.2 match
Precise near-black luminance steps alongside cyan γ2.2 target bars. The height of each cyan bar shows what the brightness should look like at that level for a perfect γ2.2 display. If the visible brightness of a strip is much brighter or darker than its target bar, gamma is incorrect in that range.
WHAT TO LOOK FOR
- Visible brightness matches cyan bar height: Accurate gamma — dark detail well-preserved
- Strips appear brighter than bars: Gamma < 2.2 — shadows lifted, image looks washed out
- Strips appear darker than bars: Gamma > 2.2 — shadows crushed, dark detail lost
💡 Most monitors ship with γ2.2 or sRGB preset. Use the gamma mode selector in Settings to switch between γ2.2, γ2.4 (cinema), and sRGB targets.
UNIFORMITY GRID
UNIFORMITY
Target: All 9 zones equal
A 3×3 grid of 9 labelled zones (TL, TC, TR, ML, MC, MR, BL, BC, BR) all showing dark gray (rgb 12,12,12). Look for brightness or colour differences between zones — especially corner zones vs. the centre. Use the Pixel Sampler to measure exact values in each zone for scientific comparison.
WHAT TO LOOK FOR
- All zones identical: Excellent panel uniformity (>95%)
- Corners slightly brighter: Common LCD backlight edge-bleed — <10% difference is acceptable
- One zone noticeably different: Poor uniformity or panel defect — may require replacement
💡 Sample each zone with the pixel tool. A difference of <5 in the grey value (e.g. 10 vs 15) is typical; >10 is noticeable in daily use.
UNDERSTANDING YOUR SCORE
S+
90 – 100
Reference-grade display. Excellent black levels, no visible crush, uniform panel, accurate gamma. Ideal for creative work, colour grading, and cinema.
A
80 – 89
Very good performance. Minor IPS glow or slight bleed in extreme conditions. Suitable for all content including gaming and HDR streaming.
B
70 – 79
Good performance. Some shadow detail loss or moderate bleed visible in dark rooms. Fine for gaming, office, and bright content.
C
60 – 69
Average. Noticeable black crush or bleed. Dark scenes may lack depth. Consider recalibration via OSD or hardware calibrator.
D
50 – 59
Below average. Significant issues with shadow detail or uniformity. May impact enjoyment of dark games, films, or night photography.
F
< 50
Poor black level performance. Severe crush, heavy bleed, or major gamma deviation. Review OSD settings, consider professional calibration.
RATING SYSTEM EXPLAINED
Score ≥ 80 — Meets or exceeds the expected specification for this panel type. No action needed.
Score 60–79 — Within normal performance range. Minor deviations that are unlikely to affect typical usage.
Score 40–59 — Noticeable issues. Recalibration or OSD adjustments recommended. May impact dark content.
Score < 40 — Significant problem detected. Hardware calibration or panel replacement may be needed.
HOW SCORES ARE CALCULATED
OBJECTIVE TESTS — Near-Black Gradient, Black Crush, Gamma, Color Bias, Uniformity, and ANSI Checkerboard are measured automatically using canvas pixel analysis. The tool draws each pattern, samples pixel values, and compares them to mathematically expected values.
SUBJECTIVE TESTS — Backlight Bleed and OLED ABL tests depend on your visual observation and star rating input. These cannot be measured by software — your eyes are the sensor.
WEIGHTED FINAL SCORE — Each test is weighted by importance: Pointer Chase ×2.5, Near-Black ×2, Crush ×2, Bleed ×1.5, Gamma ×1.5, Uniformity ×1.5, then averaged into a 0–100 score.
SUBJECTIVE TESTS — Backlight Bleed and OLED ABL tests depend on your visual observation and star rating input. These cannot be measured by software — your eyes are the sensor.
WEIGHTED FINAL SCORE — Each test is weighted by importance: Pointer Chase ×2.5, Near-Black ×2, Crush ×2, Bleed ×1.5, Gamma ×1.5, Uniformity ×1.5, then averaged into a 0–100 score.
KEYBOARD SHORTCUTS
F
Open current pattern in fullscreen
Esc
Exit fullscreen mode
→
Next test pattern (in fullscreen)
←
Previous test pattern (in fullscreen)
Space
Start / Stop test suite
R
Reset all results
1–9
Jump to pattern 1 through 9 directly
FULLSCREEN HUD CONTROLS
BRIGHTNESS SLIDER
Adjusts a CSS opacity overlay on the fullscreen canvas. Useful to fine-tune perceived luminance when testing at different ambient lighting levels. Does not change your monitor brightness setting.
Adjusts a CSS opacity overlay on the fullscreen canvas. Useful to fine-tune perceived luminance when testing at different ambient lighting levels. Does not change your monitor brightness setting.
ZOOM BUTTON
Toggles a 2× zoom state on the fullscreen pattern — useful for inspecting fine step gradients at close range on large monitors. Click any area to sample its exact pixel value.
Toggles a 2× zoom state on the fullscreen pattern — useful for inspecting fine step gradients at close range on large monitors. Click any area to sample its exact pixel value.
HUD AUTO-HIDE
The fullscreen HUD automatically hides after you move the cursor away. Hover near the bottom of the screen to reveal it. The cursor is also hidden during fullscreen to prevent it from affecting your visual judgement of dark areas. Press Esc at any time to exit.
The fullscreen HUD automatically hides after you move the cursor away. Hover near the bottom of the screen to reveal it. The cursor is also hidden during fullscreen to prevent it from affecting your visual judgement of dark areas. Press Esc at any time to exit.
PIXEL SAMPLER
Enable "Show Pixel Luminance" in Settings, then hover over the inline canvas to activate the sampler. Click any point to read its exact RGB value, luminance percentage, hex code, and pixel coordinates. This is especially useful for:
- Measuring exact luminance in each zone of the Uniformity Grid
- Detecting colour tint by comparing RGB channels in the neutral strip of Color Bias
- Verifying exact step values in the Black Crush test
STEP COUNTER & STAR RATING
STEP COUNTER (0–16 buttons)
After viewing the Near-Black Gradient or Black Crush pattern, click the number corresponding to how many distinct steps you can see. This feeds directly into your Near-Black and Crush test scores.
After viewing the Near-Black Gradient or Black Crush pattern, click the number corresponding to how many distinct steps you can see. This feeds directly into your Near-Black and Crush test scores.
STAR RATING (1–5 ★)
Used for Backlight Bleed (Full Black pattern) and OLED ABL tests. Rate 1–5 based on what you see, then press Apply Rating. This updates the relevant benchmark row and feeds into your overall score.
Used for Backlight Bleed (Full Black pattern) and OLED ABL tests. Rate 1–5 based on what you see, then press Apply Rating. This updates the relevant benchmark row and feeds into your overall score.
CALIBRATION TIPS BY PANEL TYPE
🖥️ IPS / NANO-IPS
- Expected: IPS glow in corners in dark room — normal, not a defect
- Set gamma to sRGB or γ2.2 for accurate near-black
- Avoid "Black Level Boost" features — these add grey to blacks
- Keep brightness at 100–150 nits for best black perception
🖥️ VA PANEL
- Best native black levels of all non-OLED — expect near-perfect bleed test
- Watch for "black smear" in motion — not tested here but relevant to dark content
- Local dimming VA panels may show slight zone boundaries in uniformity test
- Shadow detail should score ≥13/16 — push γ2.2 for best results
✨ OLED / AMOLED
- True black (0 nit) — should score PASS on all black/bleed tests
- ABL dimming on white APL test is expected — rate 4–5★ unless it's very aggressive
- Watch for pixel-level non-uniformity ("OLED grain") in near-black gradient
- Avoid running static test patterns for extended periods — risk of temporary burn-in
💠 MINI-LED
- Excellent black levels close to OLED — expect high scores on gradient tests
- ANSI checkerboard may show halo around white squares — zone-limited dimming artifact
- Uniformity test may show slight zone boundaries at very low grey values
- No ABL concerns — run at full brightness for best shadow detail results
FREQUENTLY ASKED QUESTIONS
Why does my score differ between runs?
Automated scores for near-black and gamma tests depend on canvas pixel sampling, which can vary slightly due to browser colour management, display colour profile, and sub-pixel rendering. For most reliable results, use the manual step counter and star rating after viewing each pattern in fullscreen.
My near-black steps look different in fullscreen vs in-page — why?
The browser window chrome, page background, and OS window compositing all affect perceived black levels. The small in-page canvas is surrounded by the page's dark background which lowers your perceived eye adaptation. Fullscreen eliminates all of this. Always use fullscreen for accurate step counts.
Does browser colour management affect results?
Yes. Chromium-based browsers (Chrome, Edge, Brave) and Firefox apply ICC colour profiles from your operating system to canvas output. This means rgb(16,16,16) in the code may be rendered differently depending on your display profile. For the most accurate testing, use a browser with a sRGB-enforced mode or test with the OS colour profile set to sRGB.
I can see all 16 steps but my monitor feels "dark" in games — why?
The test measures your display's capability to show near-black information. Your game or application may have its own gamma/shadow settings, HDR tone-mapping, or black stretch features that crush shadows independently. Check the game's "Gamma", "Shadow Detail", or "Brightness" slider — this is a software issue, not a display defect.
My backlight bleed test shows bright corners — should I return the monitor?
Some backlight bleed is normal and within panel specification for IPS and TN displays. Key questions: Is it visible during normal content (games/movies) at normal brightness? Does it distract you? If bleed is only visible in a pitch-black room at high brightness but not during use — it is within spec. If it is visible during dark game scenes at your normal brightness, you have grounds for an exchange.
Is this tool accurate enough for professional display calibration?
This tool is excellent for visual inspection and relative comparison, but cannot replace a hardware colorimeter (e.g. X-Rite i1Display, Calibrite ColorChecker) for professional work. Hardware calibrators measure absolute luminance and colour accuracy with spectrophotometric precision. Use this tool to identify obvious issues and validate calibration results, not as a primary calibration instrument.
How do I fix a colour tint in dark areas?
Open your monitor OSD → Colour Settings → Adjust individual RGB channels. If blacks look bluish, lower the Blue channel slightly. If warm/orange, lower Red. Many monitors have a "User" or "Custom" colour temperature mode for this. Advanced: use a calibration tool with a spectrophotometer to create a custom ICC profile that corrects this at the OS level.
QUICK REFERENCE — OSD FIXES
| SYMPTOM | LIKELY CAUSE | OSD FIX |
|---|---|---|
| First 3–4 black steps invisible | Black crush / clipping | Lower Black Level, Shadow, or turn off Dark Stabilizer |
| All blacks look grey/washed | Elevated black floor | Lower Brightness; check "Black Level" is at minimum |
| Shadows look crushed / flat | Gamma too high (γ > 2.4) | Switch gamma preset to γ2.2 or sRGB |
| Image looks washed out in dark | Gamma too low (γ < 2.0) | Increase gamma, or use cinema/film preset |
| Bluish or warm dark areas | White balance offset | Adjust User R/G/B colour channels in OSD |
| Corner glow (IPS) | IPS glow — normal | No fix — inherent to IPS technology; reduce brightness |
| Bright edge streaks (bleed) | Backlight bleed | Reduce brightness; may resolve or require panel exchange |