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Creating Input Profiles

Creating Input Profiles. (Color managing your scanner and digital camera). How do cameras see color?. A typical digital camera image sensor is actually a grayscale analog device The sensor is made up of light-sensitive photosites (corresponding to pixels)

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Creating Input Profiles

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  1. Creating Input Profiles (Color managing your scanner and digital camera)

  2. How do cameras see color? • A typical digital camera image sensor is actually a grayscale analog device • The sensor is made up of light-sensitive photosites (corresponding to pixels) • The photosites are covered by a pattern of color filters

  3. The Bayer Pattern:

  4. The Bayer Pattern:

  5. The Analog to Digital Converter • The ADC changes the analog signal into a digital numerical value (still one color per pixel) • If set to raw capture, the camera simply records these values along with metadata tags to the memory card

  6. The Image Processing Pipeline • If raw, then the raw conversion software then produces the image’s color (among other things) by interpolating the existing color data • If jpeg, then this process is done in-camera

  7. Scanners are simpler • They also capture color data using color filters and an image sensor, but they capture all three primary colors at every pixel • No interpolation of color data

  8. Difficulties in creating input profiles • Scanner profiles are actually pretty easy • They have a fixed light source • Exposure doesn’t change • Usually scan limited gamut sources such as printed materials

  9. Difficulties in creating input profiles • Cameras can be a pain • Unlimited possible light sources • Varied exposure by design • Vastly varied spectral stimuli • Infrared/Ultraviolet sensitivity? • Can require multiple color profiles

  10. The Good News • In many VR contexts, cameras are treated similarly to scanners • Copystand/controlled lighting • Fixed exposure/white balance • Limited gamut source material

  11. Profiling Needs

  12. Profiling Needs • Target (reflective or transparency) • Target description file • Software capable of creating an input profile

  13. Scanner Profiling • Make sure scanner has had a chance to warm up (half hour) • Turn off all auto correction options in scanning software

  14. Turn off all auto correction options in scanning software

  15. Scanner Profiling • Save settings for future use (need to use same settings for future scans) • Scan, save as tif (don’t embed profile)

  16. Scanner Profiling • Straighten and crop, if necessary (get this right at the time of scan, if possible) • Clone out dust or scratches in Photoshop, if necessary

  17. Set resulting profile as default in scanning software

  18. Set resulting profile as default in scanning software • If that’s not possible, create a Photoshop action to ASSIGN your profile to future scans • Be sure to CONVERT profile to standard Adobe RGB or sRGB before any color or tonal editing

  19. ProPhoto RGB Profile (similar to a camera or scanner custom profile) --------Converted to--------- Adobe RGB Profile (commonly used in photographic applications) --------Converted to--------- sRGB Profile (the most common colorspace; for all intents and purposes, the colorspace of the web)

  20. Digital camera profiling (jpg) • Very similar to scanner profiling • Make sure lighting is even • Set a custom white balance • Set optimal exposure (check RGB histograms, if available)

  21. Digital camera profiling (raw) • Not just profiling the camera – also raw converter • Raw converter already contains profiles, but profiles can ignored and replaced or, • Raw converter can be calibrated

  22. Editing profiles • Use software capable of editing input profiles to make color adjustments to the scanned/shot image (which will then be applied to the profile • Or, fake it – use photoshop to make opposite changes to your scanned/shot target, then rebuild the profile • Either approach involves some trial and error

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