Sharpness test
Single-pixel lines and checkerboards — the harshest patterns you can feed a display. At native resolution with no scaling they look perfectly crisp; any blur, moiré, or color shimmer means something in the chain is resampling the picture. Click or press → to change patterns, Esc to exit.
Sharpness FAQ
- Why do the patterns look blurry or wavy?
- Every pattern here is built from single-pixel lines, so it's only crisp when each pixel of the signal lands on a whole number of physical pixels. A monitor running below its native resolution, fractional OS scaling (125%, 150%), or browser zoom forces resampling — lines smear into gray, and checkerboards break into wavy moiré. Set the display to native resolution and the browser to 100% zoom, and the patterns snap into focus.
- The lines are sharp but shimmer with faint colors — why?
- Thin black-and-white lines can pick up color fringes from the panel's subpixel structure, especially on the vertical line screen where each white line is one red-green-blue triplet wide. Mild fringing at normal viewing distance is a property of how LCDs and OLEDs work, not a defect. Strong rainbow banding, though, usually means a scaler or TV 'sharpness' filter is processing the image.
- What should I check on a TV used as a monitor?
- TVs process the incoming picture by default, and this test makes it obvious. If the checkerboards look crunchy, haloed, or unstable, turn the TV's sharpness control down (often the neutral setting is 0 or 50, not maximum), disable noise reduction, and switch the input to PC or Game mode so the panel gets the signal pixel-for-pixel. Overscan — edges of the pattern cut off — means the TV is zooming the picture; look for a 'just scan' or '1:1' aspect setting.