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Human Vision

Human Vision. Nov 15.2012 Wu Pei. The eye. Optical system. Cone and Rod Vision:. In a sense, each of us has two visual systems; the photopic system functions in lighted conditions; the scoptopic system functions in dim light

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Human Vision

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  1. Human Vision Nov 15.2012 Wu Pei

  2. The eye

  3. Optical system

  4. Cone and Rod Vision: • In a sense, each of us has two visual systems; the photopic system functions in lighted conditions; the scoptopic system functions in dim light • Cones mediate photopic vision; rods mediate scotopic vision; this is called the duplexity theory of vision

  5. Distribution of cone and rod

  6. Blind point

  7. Spatial resolution •  4.5 million cone cells and 90 million rod cells in the human retina in average. • High resolution in middle and low resolution in edge, highest at fovea, about 1.2'. • Field of view: best resolution horizontal 35°and vertical 20° • In all: 1750*1000 in best resolution zone.  About 5-15 megapixel whole field

  8. Qualitative representation of visual detail using a single glance of the eyes.

  9. Time resolution • Persistence of vision: an afterimage is thought to persist for approximately one twenty-fifth of a second on retina. • Fps: frames per second • The mechanism of film system.

  10. Why game need better fps than movie • Movie: 24fps TV: 25fps • Game: 59/60fps

  11. Answer Real video Game

  12. Sensitivity to light • Human eye can is self-adaptive to differed light intensity by adjusting rhodopsin concentration.

  13. Light sensitivity

  14. Evolutionary perspective • Our vision is optimized for receiving the most abundant spectral radiance our star emits.  

  15. Compared with camera

  16. Contrast sensitivity

  17. Color Depth • True color :8*3=24 bits • HDR: 32*3=96 bits • HDR use float but not fixed point number for luminance ranges from 10-4 to 108 . In practice 10bit to encode luminance and 8bit for hue is enough for eliminating quantization error.

  18. Generating HDR Image

  19. Color banding

  20. Hints for video coding • Human eye is less sensitive to chrominance signal than to luminance signal (U and V can be coarsely coded) • Human eye is less sensitive to the higher spatial frequency components • Human eye is less sensitive to quantizing distortion at high luminance levels

  21. Estimating bandwidth of eye • Input:24bit*10Mpixel*24fps=720MB/s • Output: ~100kB/s • Compare: H.264,1080p:1.5MB/s

  22. How the visual information encoded • The process of neuron development is a process of “training”.

  23. Encoding and illusion • Illusion means visually perceived images that differ from objective reality. • Generally visual encoding is a lossy coding. So look at the illusion will be helpful to know the encoding process.

  24. Mach band: Lateral inhibition

  25. More example: Hermann grid

  26. Thank You

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