Why human eye is better than both digital and film cameras
May 4th, 2011 - 1:44 pm ICT by ANIWashington, May 4 (ANI): Nearly 50 years ago, physiologists described the human retina’s tricks for improving contrast and sharpening edges in an image, while also capturing faint detail.
But now, new experiments by neurobiologists at University of California, Berkeley and the University of Nebraska Medical Center in Omaha show how the eye achieves this without sacrificing shadow detail.
“Lateral inhibition” (when light-sensitive nerve cells in the retina inhibit dozens of their near neighbors) was first observed in horseshoe crabs by physiologist H. Keffer Hartline.
In the current study, Richard Kramer and former graduate student Skyler L. Jackman discovered that during lateral inhibition, horizontal cells not only inhibit their neighbors (negative feedback), but also boost the response of the nearest cells (positive feedback).
That extra boost preserves the information in individual light detecting cells the rods and cones thereby retaining faint detail while accentuating edges.
By locally offsetting negative feedback, positive feedback boosts the photoreceptor signal while preserving contrast enhancement. Positive feedback is local, whereas negative feedback extends laterally, enhancing contrast between center and surround.
The study is forthcoming in the online, open access journal PLoS Biology. (ANI)
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Tags: contrast enhancement, film cameras, hartline, horizontal cells, horseshoe crabs, human retina, keffer, lateral inhibition, nebraska medical center, negative feedback, nerve cells, physiologist, plos biology, richard kramer, rods and cones, sensitive nerve, shadow detail, university of california berkeley, university of nebraska, university of nebraska medical center