Phenomenal brightness {brightness} {luminosity} relates to logarithm of total stimulus-intensity energy flux from all wavelengths. Surfaces that emit more lumens are brighter. On Munsell scale, brightness increases by 1.5 units if lumens double.
properties: reflectance
Surfaces that reflect different spectra but emit same number of lumens are equally bright.
properties: reflectivity
For spectral colors, brightness is logarithmic, not linear, with reflectivity.
factors: adaptation
Brightness depends on eye adaptation state. Parallel pathways calculate brightness. One pathway adapts to constant-intensity stimuli, and the other does not adapt. If two same-intensity flashes start at same time, briefer flash looks dimmer than longer flash. If two same-intensity flashes end at same time, briefer flash looks brighter than longer flash {temporal context effect} (Sejnowsky). Visual system uses visual-stimulus timing and spatial context to calculate brightness.
factors: ambient light
Brightness is relative and depends on ambient light.
factors: color
Light colors change less, and dark colors change more, as source brightness increases. Light colors change less, and dark colors change more, as color saturation decreases.
factors: mental state
Brightness depends on mental state.
brightness control
Good brightness control increases all intensities by same amount. Consciousness cannot control brightness directly. Television Brightness control sets "picture" level by increasing input-signal multiple {gain, brightness}. If gain is too low, high-input signals have low intensity and many low-input signals are same black. If gain is too high, low-input signals have high intensity and many high-input signals are same white. Television Brightness control increases ratio between black and white and so really changes contrast.
Consciousness>Consciousness>Sense>Vision>Physiology>Intensity
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Date Modified: 2022.0224