Spatio-chromatic contrast sensitivity under mesopic and photopic light levels

Area of Science:

• Visual neuroscience
• Human visual system function

Background:

• Contrast sensitivity functions (CSFs) are crucial for understanding visual perception at different spatial scales.
• Limited data exists on how achromatic and chromatic contrast sensitivity changes across mesopic to photopic ranges, especially under outdoor lighting conditions.

Purpose of the Study:

• To characterize the CSF for both achromatic and chromatic stimuli across a wide range of background luminance levels (0.02 to 7,000 cd/m²).
• To investigate the differential effects of luminance on achromatic versus chromatic contrast sensitivity.

Main Methods:

• Measured contrast sensitivity using Gabor patches (0.125 to 6 cpd) on a high dynamic range (HDR) display.
• Assessed sensitivity in achromatic, red-green (L/M-cone opponent), and yellow-violet (S-cone opponent) color directions.
• Adapted observers to fixed background luminances ranging from 0.02 to 7,000 cd/m².

Main Results:

• Achromatic contrast sensitivity increased up to 200 cd/m² background luminance, then sharply declined at higher levels.
• Chromatic contrast sensitivity showed no significant drop at higher luminance levels.
• Developed a computational model predicting luminance-dependent CSFs for achromatic and chromatic stimuli.

Conclusions:

• Background luminance differentially impacts achromatic and chromatic contrast sensitivity.
• Achromatic vision is more susceptible to luminance saturation than chromatic vision.
• The developed model offers a predictive tool for visual performance across diverse lighting conditions.