How does the visual system distinguish between illuminance and reflectance?

Area of Science:

• Visual perception
• Psychophysics
• Color science

Background:

• The human visual system's ability to perceive brightness is complex.
• Understanding the factors influencing brightness constancy is crucial for visual science.

Purpose of the Study:

• To investigate whether the visual system can differentiate between illuminance and reflectance.
• To explore the underlying mechanisms of brightness constancy across various scales.

Main Methods:

• Experiments utilizing pattern and fusion strengths as distinct measures.
• Microscopic observation of gray papers to analyze surface properties.

Main Results:

• The visual system demonstrated the ability to distinguish between illuminance and reflectance.
• Luminance is proposed to have two aspects: photon density and microscopic reflectance proportion.
• Brightness constancy was observed across macroscopic and microscopic pattern sizes.

Conclusions:

• Brightness constancy is maintained irrespective of pattern scale, from visible to microscopic levels.
• The strength of fusion presents a novel and promising metric for brightness analysis.