What is the lowest intensity of light that generates any stimulus in the human eye? In what wave length range?
IIRC you can actualy see single photon events with the eye rod system.damitr said:What is the lowest intensity of light that generates any stimulus in the human eye? In what wave length range?
Another related concept is the dynamic range of our eye..... neural filters only allow a signal to pass to the brain to trigger a conscious response when at least about five to nine (photons) arrive within less than 100 ms. If we could consciously see single photons we would experience too much visual "noise" in very low light, so this filter is a necessary adaptation....
Across the whole visible spectrum, what wavelength are we most sensitive to? I found one reference (ref03) which is in agreement with Warren.At any given instant, the retina can resolve a contrast ratio of around 100:1 (about 6 1/2 stops). As soon as your eye moves (saccades) it re-adjusts its exposure both chemically and by adjusting the iris. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) are mostly complete in thirty minutes. Hence, over time, a contrast ratio of about 1,000,000:1 (about 20 stops) can be resolved. The process is nonlinear and multifaceted, so an interruption by light nearly starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like alcohol or tobacco.
A light-adapted eye typically has its maximum sensitivity at around 555 nm, in the green region of the optical spectrum