This is a structured list of known or lesser-known screen rendering mechanisms that can potentially cause neurological or visual discomfort, especially for hypersensitive users. Some are well-documented (like PWM or dithering), others are rarely discussed outside engineering or GPU driver development circles.
🔁 1. Temporal Dithering / Frame Rate Control (FRC)
• Purpose: Simulates more colors by rapidly oscillating between two nearby colors.
• Issue: Produces micro-flickering invisible to the eye, but neurologically triggering.
• ✅ Already identified as problematic by many sensitive users.
🌗 2. Spatial Dithering
• Purpose: Simulates missing colors by spatially dispersing different-colored pixels.
• Effect: “Grainy” texture or noise in gradients.
• Problem: Can cause eye strain or visual discomfort if poorly implemented.
• ❗ Often active even if temporal dithering is disabled.
🌈 3. “8-bit + FRC” Fake True Color
• Description: Many so-called 8-bit panels are actually 6-bit + FRC, tricking the OS and GPU into enabling dithering and other enhancements.
• Issue: Hidden dithering persists even on allegedly high-end screens.
🧠 4. Font Smoothing / Subpixel Rendering (e.g., ClearType, FreeType)
• Purpose: Smooths font edges by using the individual RGB subpixels.
• Problem: Can create colored fringes, blur, or subtle strain around text.
• Examples:
• ClearType (Windows) — known to be disturbing for some.
• FreeType2 (Linux) — configurable, but not always intuitive to adjust.
• 💡 Can be disabled, but not always well documented.
💡 5. Compositing and Window Manager Effects
• Purpose: Adds window shadows, blur, transparency, hover animations, etc.
• Problem: GPU rendering for each frame introduces potential flicker, tearing, or shimmer effects.
• Examples:
• KWin (KDE), Mutter (GNOME), Picom / Compton (X11)
🔄 6. VSYNC, Double/Triple Buffering, Tearing
• Purpose: Synchronizes display refresh to prevent screen tearing.
• Problem: Improper buffering causes frame skips, flicker, or inconsistent visual flow.
🔧 7. Gamma Correction & Color Profiles (ICC)
• Purpose: Adjusts color accuracy via GPU or monitor LUTs.
• Problem: White becomes overly intense or unstable; transitions may shimmer.
• ICC profiles can alter GPU output even on neutral content.
⚡ 8. Overdrive / Response Time Compensation
• Purpose: Accelerates pixel transitions to reduce motion blur.
• Problem: Can create ghosting or inverse ghosting artifacts, even flickering.
• ❗ Found in nearly all modern LCD monitors.
⚙️ 9. Pulse Width Modulation (PWM)
• Purpose: Dims LED brightness by switching them on and off very rapidly.
• Problem: Causes invisible flicker, sometimes inducing headaches or eye strain.
• ⚠️ Even high-frequency PWM (10kHz+) can be problematic for some users.
👀 10. Dynamic Brightness / Contrast / Local Dimming
• Purpose: Adjusts screen lighting in real time based on content.
• Problem: Creates involuntary brightness changes, which can trigger discomfort.
💻 11. Color Banding
• Description: Missing smooth gradients result in visible “steps” between shades.
• Problem: Often worsened by bad dithering or low color depth.
🧬 12. Backlight Uniformity / Mura Effect
• Description: Uneven backlighting creates zones of differing brightness.
• Problem: Subtle visual noise that fatigues the eye.
• Common on lower-end IPS panels.
🔁 13. Interpolation / Upscaling / GPU Post-processing
• Description: Filters applied by GPU (sharpening, interpolation, color boost).
• Problem: Creates imperceptible distortions, or flicker, often mistaken for eye strain.
🌀 14. Variable Refresh Rate (FreeSync, G-Sync)
• Purpose: Matches monitor refresh rate with GPU frame output.
• Problem: May introduce inconsistencies in rendering — shimmering or stutter.
🕹️ 15. Proprietary GPU Drivers (NVIDIA/AMD)
• Problem: Some drivers force dithering or color processing with no user override.
• Example: xrandr or xcalib changes may be ignored on certain hardware.
👻 16. Light Bleed / Glow / IPS Glow
• Problem: Unwanted brightness around corners or on dark backgrounds.
• Visual annoyance: Can disrupt peripheral vision or visual comfort.
📋 Summary Table
Phenomenon Well-Known? Invisible? Problematic? Disable Possible?
Temporal Dithering ✅ Yes ✅ Yes ✅ Yes ❌ Rarely
Spatial Dithering ⚠️ Somewhat ✅ Yes ⚠️ Yes ✅ Sometimes
Subpixel Rendering ⚠️ Somewhat ✅ Yes ⚠️ Yes ✅ Yes
PWM Flicker ✅ Yes ✅ Yes ✅ Yes ❌ Often Not
Overdrive ⚠️ Somewhat ✅ Yes ✅ Yes ✅ Sometimes
Compositing Effects ⚠️ Somewhat ✅ Yes ⚠️ Yes ✅ Usually
Gamma/ICC ❌ Rare ✅ Yes ✅ Yes ✅ Yes
If a developer or group were to build a Linux distribution tailored to screen-sensitive users, this list would form a base checklist of features and technologies to disable or control at every level of the graphical stack —