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Understanding Color Management in Digital Cameras and Scanners

This guide explores how digital cameras and scanners perceive color, detailing their respective sensors and profiles. Digital cameras use grayscale analog sensors with color filters, while scanners capture primary colors without interpolation. We highlight the challenges of creating input profiles for both devices due to varied light sources and exposure conditions. Learn about the importance of consistent settings, proper profiling techniques, and editing profiles for accurate color output. This resource is essential for photographers and graphic designers aiming to enhance their workflow and achieve precise color reproduction.

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Understanding Color Management in Digital Cameras and Scanners

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Presentation Transcript

  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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