This is useful for observing temporal behaviors of your display refresh rate. Faster moving line is better/easier for detecting artifacts.

• Useful for pursuit camera or high speed photography for scientific Blur Edge measurement & analysis.
• Useful to detect PWM dimming in displays at lower brightness. You may see multiple vertical lines from PWM-interrupted persistence motion blur.
  
• Useful to detect DLP rainbow artifacts, or other temporal noise on Plasma/DLP displays.
  
• Tilting of the line may be visible in full screen during low refresh rates (60Hz) on some displays. See Scan Skew Test.