TV Overscan & 1:1 Pixel Mapping
Edge cropping, HDMI scaling, Just Scan settings, and desktop sharpness degradation.
Overscan is a legacy television processing behavior that crops 2% to 5% off the outer edges of an incoming video signal and scales the remaining picture up, cutting off taskbars and blurring desktop pixels.
Why It Matters
Connecting a PC, laptop, or gaming console to a television with overscan enabled ruins text sharpness and UI usability because single digital pixels are stretched across multiple physical display pixels instead of mapping 1:1.
What Users Should Look For
- The Windows taskbar, start button, or window close buttons cut off by the television frame
- Blurry, smudged desktop fonts that look far softer than on a standard computer monitor
- A fuzzy halo or ringing artifacts along the edges of high-contrast text and icons
- Outer 1-pixel border test lines completely invisible when viewing in fullscreen
How to Test This Parameter
- 1Open the TV Overscan & 1:1 Pixel Mapping Test in Screen Tester and toggle Fullscreen mode (press F11)
- 2Check if all four colored 1px, 2px, and 5px outer border lines are fully visible around the top, bottom, left, and right edges
- 3Inspect the central and corner checkerboard patches for moiré shimmering or distortion
Technical Testing Boundaries & Methodology
Screen Tester emphasizes transparency: we clearly delineate between what web browser engines can mathematically inspect versus what requires specialized physical laboratory probes.
- ✓Fullscreen calibrated 1-pixel outer border boundaries and corner registration arrows
- ✓High-frequency 1:1 alternating black and white checkerboard test patches
- ✓User visual verification of edge cut-off under unscaled browser canvas presentation
- ✕Television internal EDID profile negotiation or manufacturer picture preset mode names
- ✕HDMI port hardware input labeling (e.g., whether the port is labeled 'PC' or 'Game')
- ✕Internal scaler spatial filtering algorithms inside the television SoC
The Historical Origin of Overscan
In the cathode-ray tube (CRT) era, analogue broadcast video signals contained electrical timing noise, blanking intervals, and broadcast data (like closed captions) along the extreme outer edges of the frame.
Television manufacturers engineered CRT electron beams to intentionally scan 5% beyond the visible tube bezel (overscan) to hide this ugly edge noise from viewers.
When digital flat panels arrived, manufacturers kept overscan enabled by default on TV HDMI inputs to maintain backwards compatibility with analogue cable broadcasts, creating a headache for modern digital PC inputs.
Common Causes
- •Television picture aspect ratio set to '16:9' or 'Standard' instead of 'Just Scan', 'Screen Fit', or '1:1'
- •HDMI input port on the television not renamed or designated as 'PC' in television input settings
- •GPU driver control panel (NVIDIA/AMD/Intel) has 'Desktop Resizing' or underscan scaling enabled
- •AV receiver or HDMI switch applying secondary video processing to the pass-through signal
Recommended Next Steps
- →On your TV remote, open Picture / Screen Settings, find Aspect Ratio, and change it to 'Just Scan', 'Screen Fit', 'Dot by Dot', or 'Original'
- →In the TV input source list, edit the HDMI icon and name to 'PC' (this automatically disables overscan and post-processing on LG, Samsung, and Sony TVs)
- →Open your GPU control panel and reset desktop size / scaling adjustments to 100% with no underscan
Frequently Asked Questions
Why does my PC desktop look blurry when connected to a 4K TV?
If overscan is active, the TV crops the outer edge of your 3840 × 2160 signal and scales the remaining ~3650 × 2050 image up to fill the glass, forcing bilinear interpolation across every single pixel. Enabling 1:1 pixel mapping restores crisp, sharp text.
What is the overscan setting called on different TV brands?
LG calls it 'Just Scan: On'. Samsung calls it 'Picture Size: Screen Fit'. Sony calls it 'Wide Mode: Full' with 'Display Area: Full Pixel'. Panasonic calls it '1:1 Pixel Mapping' or 'HD Size: 2'.