"Magnitude estimation a technique standardly applied in psychophysics to measure judgments of sensory stimuli (Stevens 1975). The magnitude estimation procedure requires subjects to estimate the magnitude of physical stimuli by assigning numerical values proportional to the stimulus magnitude they perceive. Highly reliable judgments can be achieved for a whole range of sensory modalities, such as brightness, loudness, or tactile stimulation."
By which I mean, is there any objective measure of human perceived luminance?