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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 l.jpg

Creating Input Profiles

(Color managing your scanner and digital camera)


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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




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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


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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


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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


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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


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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


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The Good News

  • In many VR contexts, cameras are treated similarly to scanners

  • Copystand/controlled lighting

  • Fixed exposure/white balance

  • Limited gamut source material



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Profiling Needs

  • Target (reflective or transparency)

  • Target description file

  • Software capable of creating an input profile


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Scanner Profiling

  • Make sure scanner has had a chance to warm up (half hour)

  • Turn off all auto correction options in scanning software



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Scanner Profiling

  • Save settings for future use (need to use same settings for future scans)

  • Scan, save as tif (don’t embed profile)


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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



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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


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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)


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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)


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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


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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