Even Closer to the Human Eye

Mechanisms of the Human Eye to See with High Sensitivity

Index

Mechanisms of the Human Eye to See with High Sensitivity

1: Bipolar cell 2: Cone 3: Rod

As explained in the previous section, photoreceptor cells of the human eye are composed of rods and cones. Rods play an active role in dark places.

They are ultrasensitive, capable of responding even to a single photon, and are said to be about 120 million of them in one eye. While it is generally thought that brightness is adjusted by the opening and the closing of the pupil (corresponding to the aperture of the camera lens), this is true only under bright conditions. When it becomes dark, the pupil dilate to take in as much light as possible. Furthermore, the principle role is switched over from cone (dominant when bright) to rod (dominant when dark). Although rods are highly sensitive, they are not involved in sensing color, as opposed to cones, which form the basis of color vision, and they are low in sensitivity. The human eye misjudges colors in dark places because the function of cones to perceive color significantly drops when the amount of light falls below a certain level.

On the other hand, even though digital cameras may generate “false colors,” they are able to reproduce nearly the exact colors. In addition, when light becomes minimal, the human eye has the characteristic of repetitively processing the information perceived by multiple photoreceptor cells (rods and cones) through successive integration. Particularly rod cells where multiple photoreceptor cells act as a single cell to increase sensitivity by sacrificing the ability to see subjects in fine details (resolution). The “Pixel Fusion Technology” of EXR is thought to be similar to this mechanism.

EXR Pixel Binning
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