Brightness versus apparent contrast. 2: Large-field asymmetry.

Area of Science:

• Visual perception
• Psychophysics
• Photometry

Background:

• Distinguishing between brightness and apparent contrast is crucial for understanding visual perception.
• Previous research has explored luminance perception but often conflates brightness and contrast.

Purpose of the Study:

• To investigate the quasi-static perception of brightness and apparent contrast.
• To differentiate the perceptual attributes of brightness and apparent contrast.
• To analyze the effectiveness of luminance increments versus decrements on perception.

Main Methods:

• Experiments were conducted on a foveal 1-degree disk.
• Stimuli were presented as luminance increments or decrements against a 300 cd.m-2 background.
• Data were analyzed using Stevens' power function and standard contrast formulas.

Main Results:

• Brightness and apparent contrast are distinct perceptual attributes.
• Luminance increments are more effective than decrements for equal brightness differences.
• For equal apparent contrast, increments and decrements are similarly effective up to 100 cd.m-2, with decrements becoming more effective at higher values.
• Both brightness and apparent contrast can be modeled using power functions of luminance differences.

Conclusions:

• Brightness and apparent contrast are separable perceptual dimensions.
• The relationship between luminance and perceived attributes is non-linear and depends on whether it's an increment or decrement.
• Power functions effectively describe the perception of brightness and apparent contrast in relation to luminance differences.