Even Closer to the Human Eye

Mechanisms of the Human Eye to Expand Dynamic Range

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Mechanisms of the Human Eye to Expand Dynamic Range

What is the dynamic range of human perception? In fact, the eye is capable of visioning up to the sixth-magnitude star for the dark part, and for the bright part, up to the brightness of the sun. The difference between the bright and the dark is said to be 108
LX (= 100 million times). Therefore, the optical sensor comprised of cones and rods controls the ability to see by compressing the light from bright objects and increasing our sensitivity to see dark objects.

1: Photopic Vision 2: Scotopic Vision
1: High Sensitivity Data 2: Low Sensitivity Data 3: Combined Processing

However, is it possible to say that the human eye possesses an extravagant dynamic range? In fact, it isn't that simple. People do not receive visual information all in a single moment. As one's perspective shifts, information are captured at an average of three times per second, and sent to the brain where information are synthesized. For example, when a person looks at a scene with light and dark contrasts, the eye shifts to see dark and light areas separately. When the brain combines them, the person would simultaneously “recognize” clarity in scene. While there is a wide range of light volume that can be detected by the retina, when speaking of an instantaneous moment of high contrast in a vision, the eye is not perceiving the object at the same time.

This mechanism of the eye is said to be very similar to “Dual Capture Technology” that optimally combines both high sensitivity and low sensitivity image data. In fact, in the terms of seeing at a glance, the EXR may be superior to the human eye.

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