ColorConverter - Technical Specifications

The Colorimetric Calculator

Introduction
Conversion flow
Input specifications
Technical specifications

ColorConverter is based on CIE 1931 (2° observer) colorimetry and on standard RGB color spaces. See CIE Colorimetry Technical Report (CIE 15:2004 3rd edition) for more info about standard colorimetry.

The color modes and spaces supported by this app are:

• RGB in these standard spaces:
  • Adobe RGB
  • CIE RGB
  • ColorMatch
  • eciRGB v2
  • NTSC RGB
  • PAL SECAM RGB
  • several ProPhoto variants, i.e.
    • ProPhoto (original, TRC gamma 1.8)
    • Melissa RGB (as ProPhoto, but TRC is the same of sRGB TRC)
    • ProStar (as ProPhoto, but TRC is L*)
    • RIMM (as ProPhoto, but TRC is gamma 1)
  • sRGB
  • WideGamut
• HSB (also called HSV)
• HSL (also called HLS)
• XYZ (CIE 1931, 2°)
• Yxy (CIE 1931, 2°)
• Helmholtz coordinates: luminance, excitation purity (pe), colorimetric purity (pc), dominant wavelenght (λd) and complementar wavelength (λc)
• Lab (CIE 1976)
• LCh (CIE 1976)

References for these color modes and spaces:

• Adobe RGB: see Adobe RGB (1998) Color Image Encoding and Bruce Lindbloom RGB Working Space Information;
• CIE RGB: seeBruce Lindbloom RGB Working Space Information and Wikipedia;
• ColorMatch: see Bruce Lindbloom RGB Working Space Information;
• eciRGB v2: see European Color Initiative website and Bruce Lindbloom RGB Working Space Information;
• NTSC RGB: see Bruce Lindbloom RGB Working Space Information;
• PAL/SECAM RGB see Bruce Lindbloom RGB Working Space Information
• Melissa RGB: see reference for ProPhoto and sRGB, because Melissa RGB has same primaries and white as ProPhoto, and same TRC (Tone Response Curve) as sRGB;
• ProPhoto: technical name of this space is ROMM RGB, see specifications on this Kodak PDF and Bruce Lindbloom RGB Working Space Information;
• RIMM is the counterpart of ROMM, in fact it has same primaries but a linear TRC, see specification on this Kodak PDF;
• sRGB see Bruce Lindbloom RGB Working Space Information
• WideGamut see Bruce Lindbloom RGB Working Space Information
• HSB and HSL are originally descripted in this classic paper of Alvy Ray Smith; see also Wikipedia, where HSB is called HSV;
• XYZ is the CIE tristimulus space for the standard observer CIE 1931 (2°), see CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 12);
• xy is the chromaticity coordinates from XYZ CIE 1931, see CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 16 and 66);;
• Lab is the CIE 1976 uniform color space L*a*b*, see CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 16 and 66);
• LCh see CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 17);
• Helmholtz coordinates: luminance, excitation purity, dominant and complementar wavelength. See CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 22);

Also are supported

• Blackbody color temperature (from K to xy) and correlated color temperature (from XYZ to K) in kelvin (K). See Robertson method on Bruce Lindbloom website.
• Inverse color temperature: mired is 1000000 / kelvin (MK-1)
• Daylight correlated color temperature (input only, from D to xy). See CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 62) and Bruce Lindbloom website.

Following standard CIE illuminants are supported (for CIE 1931 standard colorimetric observer). Tristimulus values for these illuminants are from CIE Colorimetry Technical Report (CIE 15:2004 3rd edition, p. 35)

• A
• C
• D50 CIE (tristimulus values from CIE 15:2004 edition)
• D50 ICC (tristimulus values from previous version of CIE 15, there is a difference only in the Z component)
• D55
• D65
• D75
• E

Colors are converted

• from the RGB space illuminant (first illuminant) and a reference illuminant (second illuminant), or
• from a first illuminant to a second illuminant

using different chromatic adaptation algorithms. Following chromatic adaptation transforms (CAT) algorthms are supported. Reference for these CATs is the Bruce Lindbloom website and Color Appearance Model by Mark Fairchild

• Bradford
• CAT02
• CAT97s
• CMCCAT2000
• Sharp CAT
• XYZ Scaling
• von Kries CAT (i.e. Hunt-Pointer-Estevez transformation)

ColorConverter is a project by Mauro Boscarol. For information and requests, send an email to me.