Threshold Increment (TI) is a measure of the eye's sensitivity under different lighting conditions, particularly in situations with scattered light or slight glare . It is often used in visual perception tests and research on night vision, driving safety, and lighting.
What is Threshold Increment (TI)?
TI indicates how much additional light is needed to detect an object above the detection threshold in the presence of a bright light source or background illumination.
The formula for Threshold Increment is:
whereby:
- ΔL = the additional amount of light (luminance) required to distinguish an object
- L = the original background luminance
A higher TI value means that it is more difficult to observe an object due to the presence of scattered light or a blinding source.
Applications of TI:
- Road Lighting and Traffic Safety : TI is used to analyze the effects of headlights and street lighting on the visibility of traffic signs and pedestrians.
- Aviation and Night Vision : Pilots and military personnel use TI measurements to minimize the impact of light sources on visibility in dark conditions.
- Eye examination and optics : TI tests are used to investigate conditions such as night blindness or glare tolerance .