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Probe Profile

Probe1 Profile v1.1, 11-11-04, Updated 2-22-08

The 'probe profile' (Probev1_ICCv2.icc) is syntactically a v2 ICC output device ('prtr') profile, and can be used in a workflow wherever such a profile is required. The color space of this profile is CMYK, and its PCS is Lab.

Colors processed via this profile are deliberately distorted in a systematic way, to enable visual determination of the rendering intent used when rendering ("BToA" or PCS to device transforms) and when proofing ("AToB" or device to PCS transforms). This is useful, in cases when color-management-aware software does not document the behavior.

The rendering intent transforms (BToA tags) of the probe profile ignore the a* and b* components of incoming PCS colors, and map the L* components directly to monotone tints of process colorants. (L* = 0 is rendered as maximum colorant coverage, and L* = 100 is rendered as unmarked media.) The B2A0 tag (perceptual rendering intent transform) renders the L* values as tints of pure cyan. The B2A1 tag (relative colorimetric intent transform) renders them as tints of pure magenta, and the B2A2 tag (saturation intent transform) renders them as tints of pure yellow. As such, one can visually determine the rendering transform used in a workflow by processing an image with the profile and observing the dominant hue of the rendered result.

The proofing (AToB) transforms of the probe profile modify a different perceptual dimension, i.e., lightness. These transforms are derived from color measurements of an actual device. For the perceptual (A2B0) tag, the output 1D LUTs are set such that the measured L* values are scaled and offset into the range 70 to 100. For the relative colorimetric (A2B1) tag, the L* values are scaled and offset into the range 30 to 70. For the saturation (A2B2) tag, they are scaled to the range 0 to 30.

In a proofing scenario, the rendering transform of the device being proofed (e.g., a press) is followed first by the proofing transform of the same device, and then by the rendering transform of the proofing device (e.g., a desktop printer). If the probe profile is substituted for the press profile in this scenario, one can simultaneously determine which AToB transform and which BToA transform are applied, according to the following table:

B2A0 A2B0 light cyan
B2A0 A2B1 mid-tone cyan
B2A0 A2B2 dark cyan
B2A1 A2B0 light magenta
B2A1 A2B1 mid-tone magenta
B2A1 A2B2 dark magenta
B2A2 A2B0 light yellow
B2A2 A2B1 mid-tone yellow
B2A2 A2B2 dark yellow
See examples of the effect of these Probe Profile transforms

The media white point ('wtpt' tag) of the probe profile is set to X =.75, Y = .5, and Z = .25 (a reddish color). This is an attempt to provide additional visual discriminability between the relative and absolute colorimetric intents of the proofing (AToB) transform. Determination may be made by sending a 'white' image through the workflow.

A v4 version of the probe profile is also posted as Probev1_ICCv4.icc. Technically, this is non-compliant with the v4 ICC specification, because (obviously) the media relative colorimetric intent tags are not based on real measurement data, as is required for v4 profiles. However, many CMMs and applications may not complain about this, and the v4 probe may still be useful as a workflow analysis tool. Thanks to Uwe-Jens Krabbenhoeft (Heidelberg) for converting the v2 probe to the v4 version.

Of course, these profiles are provided 'as is' and without warranty of any kind.

Further details are available as "Exploiting Pseudocolor in ICC Workflow Analysis," Abhay Sharma and John Dalrymple, Proc. IS&T 12th Color Imaging Conference, Scottsdale, AZ, Nov 9-12, 2004.

The following naming states that the Probe Profile is at version 1, while the ICC specification may be v2 or v4. The profiles are provided as compressed .sit or .zip files.



Probev2_ICCv4 Profile with MPE support

The v2 Probe profile Probev2_ICCv4.icc is similar to Probev1_ICCv4.icc with the addition of optional tags based on the MultiProcessingElement tag type (See ICC Revision 02-11-2006: Floating Point Device Encoding Range). This includes support for the new rendering intents BToD and DToB, The behaviour of the v2 Probe profile is the same as the v1 profile with the following additions:

  • The B2D0 tag (MPE perceptual rendering intent transform) renders the L* values as tints of pure red (a combination of magenta plus yellow). The B2D1 tag (MPE relative colorimetric intent transform) renders them as tints of pure green (a combination of cyan and yellow), and the B2D2 tag (MPE saturation intent transform) renders them as tints of pure blue (a combination of cyan and magenta).

  • With the MPE perceptual (D2B0) tag, the luminance output is inverted and set such that the measured L* values are scaled and offset into the range 70 to 100. The MPE relative colorimetric (DToB1) and saturation (DToB2) tags invert the output so that the measured L* values are scaled and offset into the range 33-66 and 0-33 respectively.
The following table makes it possible to determine which DToB transform and/or which DToA transform was applied.

B2A0 D2B0 inverted light cyan
B2A0 D2B1 inverted mid-tone cyan
B2A0 D2B2 inverted dark cyan
B2A1 D2B0 light magenta
B2A1 D2B1 mid-tone magenta
B2A1 D2B2 dark magenta
D2A0 A2B0 light red
D2A0 A2B1 mid-tone red
D2A0 A2B2 dark red
D2A0 D2B0 inverted light red
D2A0 D2B1 inverted mid-tone red
D2A0 D2B2 inverted dark red
D2A1 A2B0 light green
D2A1 A2B1 mid-tone green
D2A1 A2B2 dark green
D2A1 D2B0 inverted light green
D2A1 D2B1 inverted mid-tone green
D2A1 D2B2 inverted dark green
D2A2 A2B0 light blue
D2A2 A2B1 mid-tone blue
D2A2 A2B2 dark blue