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| Stare at this. What do you see? |
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1 comment:
It should go white. Then reappear after blinking:
The effect is for color/intensity compensation in your eyes. The specific mechanism is fatigue in the particular retinal cells that are responding to each part of the image.
Ever wonder why you can see colors both in daylight (strong, very bluish light) and incandescent light in your home at night (faint, very reddish light)? Your eyes have an amazing mechanism to compensate and preserve approximate chroma values and to preserve your vision despite the crazy differences in illumination.
The retinal cells that produce nerve signals for your brain deplete their internal ATP supply as they fire, resulting in a long-ish (Edit: ~ 1 minute) time constant decay of any given signal. Weak illumination -> not so much firing of the nerve -> more fuel in the cell -> more sensitivity. Likewise, strong illumination -> more firing of the nerve -> less fuel in the cell -> less sensitivity. This is what makes that image "disappear".
That effect is not a weakness, it is a strength. Your eyes are for, well, seeing things. The long time constant decay of any given signal makes your eye self-adjusting: it works in a broad range of environments with no adjustment. You can easily achieve a factor of 107 in dynamic range by walking into a dim room from bright sunlight. It is very difficult to make (say) an electronic camera do that.
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