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The Generic Sensor

The Generic Sensor. Problem: Since the sensor only records light intensity, we can’t differentiate between colors! Thus, digital cameras only record in black and white Solution: Color filtering, the most common form being the Bayer filter.

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The Generic Sensor

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  1. The Generic Sensor Problem:Since the sensor only records light intensity, we can’t differentiate between colors!Thus, digital cameras only record in black and white Solution:Color filtering, the most common form being the Bayer filter Each photosite converts lightwave energy into photo-electrons Pixels in the output image are a measure of the number of photo-electrons recorded at each photo site Sensors Light wells

  2. BAYER FILTER • Designates individual photosites to be either red, green, or blue (RGB) • Respective color filters are placed over each photosite • Thus, only the light energy corresponding to that color’s wavelength reaches the sensor • Thus the sensor can interpret the energy recorded at that photosite to be a measure of that certain color

  3. The Bayer Sensor Sensors Light wells

  4. Drawbacks of… Raw Bayer Output BAYER FILTER • Color offset- light not recorded at the same spot • -Demosaic algorithms required to interpolate missing data • Discards 2/3 of light information • -3x longer shutter speed, 3x larger aperture, 3x higher ISO Actual Image Demosiaced Bayer Output

  5. Alternative Color Filtering Technologies Bayer-like filters with different colors RGBC CYGM Same problems as Bayer filter Linear Scanning Scans a scene with RGB linear sensors Gets full light information Slow, only works for static subjecs Multi-shot approach Take three shots, each with different color filter Gets full light information Only works for static subjects, since a moving scene would change between filter switches

  6. Alternative Color Filtering Technologies in Development Three-sensor Commonly known as “3CCD” Prism splits light, 3 sensors to record R,G,B Foveon sensor Uses vertically stacked RGB sensors Collects all light at each location

  7. Color Temperature Light sources can be approximated as “black bodies” of a certain temperature Daylight: similar to 5000K black body (even light across the spectrum) Incandescent light: lower temperature (more red light, less blue) Shade/daylight: higher temperature (more blue light, less red) Human vision system makes corrections for different light sources Cameras aren’t so good at this

  8. <- What we see What cameras see -> (interpreting all wavelengths equally)

  9. White Balancing Auto-white balance White balance preset Color temperature Custom white balance RAW adjustment Last resort: color balance the JPEG

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