MadSci Network: Anatomy |
In the bright interior of the car with the dome lite on, you have the exact same problem as the camera, and a new problem as well..... Firstly, you force your eye to close its pupil adjusting for the light. This lets less light into the eye, and thus looking out at night, you see nothing, or very little. Secondly, in the light of the car, or in sunlight, if you can see colors, then you are using your color sensitive cone-vision. Cone cells of the retina come in short, medium and long spectral sensitivity bands to give you color vision. But, cones are not very light sensitive compared to rod cells (rods give us only black and white, gray scale). Rod-vision is more light sensitive, and that is why we cannot see the colors in dim lighting, but we can see at night with our rod-vision. In bright light the rod cells are so activated that they are "bleached" and not giving information. Conversely in the dark, our cone cells are not being activated as the light intensity is below the threshold required to give visual signals through the optic nerves. So, in the bright light of the car...you have bleached out your nite-vision rod cells, and closed down your pupil size to let in less light...therefore you cannot see outside. That is why in aircraft cockpits, instruments are often red-lit. The red light activates red sensitive color vision, but the rod cells are not as sensitive to red light and are not as severely bleached out, therefore the pilot can see instruments and outside. Some cars now come with dome lite filters can be used to give RED interiors. http:// ken.mitton.com/ern
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