3 ms·

I am confused by the color filter step. Is the output produced by the sensor RGB or a single value per pixel?

• ranger207 10mo ago
  It's a single value per pixel, but each pixel has a different color filter in front of it, so it's effectively that each pixel is one of R, G, or B
  • XCSme 10mo ago
    So, for a 3x3 image, the input data would be 9 values like: R G B B R G G B R ?
    • card_zero 10mo ago
      In the example ("let's color each pixel ...") the layout is: R G G B Then at a later stage the image is green because "There are twice as many green pixels in the filter matrix".
      • nomel 10mo ago
        And this is important because our perception is more sensitive to luminance changes than color, and with our eyes being most sensitive to green, luminance is also. So, higher perceived spatial resolution by using more green [1]. This is also why JPG has lower resolution red and green channels, and why modern OLED usually use a pentile display, with only green being at full resolutio [2]. [1] https://en.wikipedia.org/wiki/Bayer_filter#Explanation https://en.wikipedia.org/wiki/Bayer_filter#Explanation [2] https://en.wikipedia.org/wiki/PenTile_matrix_family https://en.wikipedia.org/wiki/PenTile_matrix_family
        • card_zero 10mo ago
          Funny that subpixels and camera sensors aren't using the same layouts.
          • nomel 10mo ago
            It would only be relevant if viewing the image at one-to-one resolution, which is extremely rare.
        • userbinator 10mo ago
          Pentile displays are acceptable for photos and videos, but look really horrible displaying text and fine detail --- which looks almost like what you'd see on an old triad-shadow-mask colour CRT.
    • deleted 10mo ago
      [deleted]
    • jeeyoungk 10mo ago
      If you want "3x3 colored image", you would need 6x6 of the bayer filter pixels. Each RGB pixel would be 2x2 grid of ``` G R B G ``` So G appears twice as many as other colors (this is mostly the same for both the screen and sensor technology). There are different ways to do the color filter layouts for screens and sensors (Fuji X-Trans have different layout, for example).
    • Lanzaa 10mo ago
      This depends on the camera and the sensor's bayer filter [0]. For example the quad bayer uses a 4x4 like: G G R R G G R R B B G G B B G G [0]: https://en.wikipedia.org/wiki/Bayer_filter https://en.wikipedia.org/wiki/Bayer_filter
• deleted 10mo ago
  [deleted]
• steveBK123 10mo ago
  In its most raw form, camera sensors only see illumination not color. In front of the sensor is a bayer filter which results in each physical pixel seeing illumination filtered R G or B. From there the software onboard the camera or in your RAW converter does interpolation to create RGB values at each pixel. For example if the local pixel is R filtered, it then interpolates its G & B values from nearby pixels of that filter. https://en.wikipedia.org/wiki/Bayer_filter https://en.wikipedia.org/wiki/Bayer_filter There are alternatives such as what Fuji does with its X-trans sensor filter. https://en.wikipedia.org/wiki/Fujifilm_X-Trans_sensor https://en.wikipedia.org/wiki/Fujifilm_X-Trans_sensor Another alternative is Foveon (owned by Sigma now) which makes full color pixel sensors but they have not kept up with state of the art. https://en.wikipedia.org/wiki/Foveon_X3_sensor https://en.wikipedia.org/wiki/Foveon_X3_sensor This is also why Leica B&W sensor cameras have higher apparently sharpness & ISO sensitivity than the related color sensor models because there is no filter in front or software interpolation happening.
  • XCSme 10mo ago
    What about taking 3 photos while quickly changing the filter (e.g. filters are something like quantum dots that can be turned on/off)?
    • itishappy 10mo ago
      > What about taking 3 photos while quickly changing the filter Works great. Most astro shots are taken using a monochrome sensor and filter wheel. > filters are something like quantum dots that can be turned on/off If anyone has this tech, plz let me know! Maybe an etalon? https://en.wikipedia.org/wiki/Fabry%E2%80%93P%C3%A9rot_interferometer https://en.wikipedia.org/wiki/Fabry%E2%80%93P%C3%A9rot_inter...
      • XCSme 10mo ago
        > If anyone has this tech, plz let me know! I have no idea, it was my first thought when I thought of modern color filters.
• wtallis 10mo ago
  The sensor outputs a single value per pixel. A later processing step is needed to interpret that data given knowledge about the color filter (usually Bayer pattern) in front of the sensor.
• i-am-gizm0 10mo ago
  The raw sensor output is a single value per sensor pixel, each of which is behind a red, green, or blue color filter. So to get a usable image (where each pixel has a value for all three colors), we have to somehow condense the values from some number of these sensor pixels. This is the "Debayering" process.