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display · evidence-led troubleshooting

Color Banding on Monitor

Use controlled visual and timing references to separate panel symptoms from scaling, mode or content problems when smooth gradients show obvious steps or bands. The result should determine which troubleshooting layer comes next.

Reviewed 2026-08-116 diagnostic steps2 official sources
Run Dead pixelsSee fault tree ↓

What this symptom means

Visible steps in a smooth gradient can come from content bit depth, GPU/output settings, compression, calibration or the panel itself.

Diagnostic principleSeparate panel defects from signal-path problems. Resolution, refresh rate, HDR, color depth, cable bandwidth, GPU output and physical panel defects can create similar symptoms but require different evidence.

Fault tree

Display fault tree

Use the observation that best matches what you can reproduce. Do not treat every cause as equally likely.

1
Active mode mismatch

Evidence: The display works but resolution/refresh is lower than expected.

Next: Check the OS active mode, GPU output, cable/port capability and monitor input mode.

2
Cable/adapter/dock limit

Evidence: Direct connection works but the dock/adapter path does not.

Next: Identify the weakest link by testing direct and then adding one component at a time.

3
Panel defect

Evidence: Pixel/line/uniformity defect stays in the same physical location across inputs and test patterns.

Next: Document with controlled patterns and compare warranty pixel policy/service guidance.

4
GPU/software path

Evidence: The symptom appears in screenshots/recordings or changes with GPU settings.

Next: Check graphics driver, color mode, scaling and output format.

Interpret the result

Evidence matrix

A test result is useful only if it changes the next troubleshooting branch.

ObservationWhat it supportsPrioritize next
Browser estimates expected refreshThe browser is receiving animation frames near the active refresh cadence.If motion still looks wrong, investigate frame pacing/content/GPU rather than only monitor specs.
Direct cable works; dock failsThe panel and source can form a working link.Dock, cable, adapter topology, DSC/MST or power-delivery interaction.
Defect fixed to one physical pixel/lineThe symptom follows panel coordinates rather than rendered content.Panel defect/warranty inspection.
Screenshot also shows artifactThe problem exists before the physical panel displays the frame.GPU, application, render pipeline or source content.

Fast baseline

Rule out the simple causes first

  1. 1

    Run the relevant DeviceOK display test in full screen and separate what is visually observed from what the browser can measure.

  2. 2

    Confirm the operating system is using the display's native resolution and intended refresh rate.

  3. 3

    Reconnect the display cable and verify the correct input/port.

Full sequence

Work from reversible checks to invasive ones

Do not diagnose the panel from a compressed screenshot or video; use a locally rendered reference pattern first.

  1. 1

    Run the relevant DeviceOK display test in full screen and separate what is visually observed from what the browser can measure.

  2. 2

    Confirm the operating system is using the display's native resolution and intended refresh rate.

  3. 3

    Reconnect the display cable and verify the correct input/port.

  4. 4

    Compare another cable, port, or device if practical.

  5. 5

    Reset unusual monitor picture-processing settings before deeper troubleshooting.

  6. 6

    For persistent physical panel defects, use the manufacturer's warranty/support criteria rather than relying only on a browser test.

Platform branches

Where the setting lives

Windows

  • Settings → System → Display → Advanced display
  • Check GPU control-panel output mode only after confirming Windows active mode
  • Test one monitor directly before MST/dock chains

macOS

  • System Settings → Displays
  • Hold Option/advanced controls only when needed to expose supported modes
  • Identify the exact Mac display-count limits before buying a dock

Hardware path

  • Connector shape does not prove bandwidth/video capability
  • Verify cable specification and input mode
  • Remove KVM/splitter/dock during baseline testing
If it works in DeviceOK

A normal controlled reference narrows the issue toward the original content, app or display mode. If the original symptom remains, keep the next checks above the hardware layer until evidence says otherwise.

If it also fails here

A fixed visual defect across controlled references and sources is stronger panel/path evidence. Compare the simplest direct connection and official diagnostic path before replacement.

Escalation threshold

When software troubleshooting has stopped being high value

  • Same panel defect across multiple inputs/sources
  • Display loses sync with multiple known-good cables
  • Burning smell, swelling or power instability
  • Physical crack/liquid damage
Safety
  • Do not open monitors or power supplies unless qualified; capacitors can retain hazardous voltage.
Changed one variable?Compare the same local gradient after changing only one link in the display path. Retest under the same condition so the result is comparable.
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