Taming unusual workflows with iccMAX Marti Maria Hewlett-Packard November 3rd, 2014 Joseph B. Martin Conference Center at Harvard Medical School* Boston, MA *Note: Neither NPES nor ICC DevCon is affiliated with Harvard University, and neither NPES nor ICC DevCon is a Harvard University program or activity.

Agenda – What is this talk about What you mean unusual color workflows? Changing viewing conditions. Measurement standards. Special connection spaces. Spectral matching. Fluorescence

What you mean unusual color workflows? Limitations in current ICC workflows

Limitations in current ICC workflows What is in previous ICC specs? Colorimetric connection spaces: XYZ or Lab CIE 1931 Standard observer (2º) D50 as white point No flare, 0º/45º geometry (M1 of ISO 13655) fixed viewing conditions (P2 of ISO 3664) Ideal reflection print (V2) or reference medium (V4) Maximum of 16 channels The reference medium is defined as a hypothetical print on a substrate with a white having a neutral reflectance of 89 %, and a density range of 2,459 3. The viewing reference is a standard viewing booth conforming to ISO 3664 viewing condition P2, using the recommended 20 % surround reflectance. This is a graphics arts and photography print appraisal environment using D50 illumination at a level of 500 lx.

New features in iccMAX Just some, not all. Colorimetric, Appearance, Spectral, Bi-Spectral and Material connection spaces Arbitrary illuminants, geometry and observers. Nonstandard viewing conditions. Up to 65535 channels.

Some differences in iccMAX profiles From the coder’s point of view

Compatibility  Backwards compatible An iccMAX CMM will be completely backward- compatible and will recognize and correctly process V2 and V4 profiles. However, iccMAX profiles are not expected to be compatible with V4 CMMs. ICC will seek to provide a reference implementation to help with iccMAX adoption.

Header changes for PCS extensions PCS field defines PCS color space for A2Bx/B2Ax tags If zero then no colorimetric PCS is used and no A2BX/B2AX tags should exist A2Bx/B2Ax tags can also be of type multiProcessElementType Colorimetric PCS can be other than D50 with 2 degree observer XYZ values of illuminant must match illuminant and observer used Spectral PCS fields added Spectral PCS field defines color space for D2Bx/B2Dx tags If zero and D2Bx/B2Dx tags exist then PCS field is used to define PCS Spectral PCS range defines wavelength range Bi-directional PCS range defines excitation range when bi-dir spectral color space is used

iccMAX new profile classes Signature Hex encoding Input Device profile ‘scnr’ 73636E72h Display Device profile ‘mntr’ 6D6E7472h Output Device profile ‘prtr’ 70727472h DeviceLink profile ‘link’ 6C696E6Bh ColorSpace profile ‘spac’ 73706163h ColorEncoding profile ‘cenc‘ 63656E63h Abstract profile ‘abst’ 61627374h NamedColor profile ‘nmcl’ 6E6D636Ch MaterialIdentification profile ‘mid ’ 6D696420h MaterialLink profile ‘mlnk’ 6d766973h MaterialVisualization profile ‘mvis’ Each class to cover a type of application. For example, Input profiles apply to devices such as digital cameras and scanners, Display apply to Monitors and Output apply to printers. In addition to the three basic device profile classes, other additional colour processing profiles are defined.

iccMAX new base types (some) icFloat16Number IEEE 16 bit floating point icFloat64Number IEEE 64 bit floating point spectralRange Starting Wavelength (icFloat16Number) Ending Wavelength (icFloat16Number) Total number of steps including start and end.

iccMAX tag Structures and tag Arrays Signature for structure type List of Tags identified by signatures Examples: brdfStruct, namedColorStruct, zeroTintStruct Tag Array Signature for array type Ordered list of tags (identified by index) Example: namedColorArray (contains one zeroTintStruct and one or more namedColorStructs)

Changing viewing conditions “There are no facts, only interpretations.” ― Friedrich Nietzsche

The problem Example: ISO 3664:2000 (viewed independently ) Uses D65 for proofing ISO 12646:2004 (directly compared to a hard copy) As well as previous ICC specs, requires D50 as illuminant. Chromatic adaptation can be used across CHAD tag, but still the color matching is done as viewed under D50

iccMAX Profile Connection Conditions (PCC) PCC information is required whenever PCS is NOT standard D50 using 2-degree observer CMM becomes responsible for converting PCS data – not profile maker Provides for interoperability to connect different viewing conditions Provides flexibility for when and how conversions are made

iccMAX viewing conditions in 3 tags spectralViewingConditions Defines the spectral power distribution of the illuminant, colour matching functions (CMF) of the observer, and the lighting levels of the surround. If different from the standard PCS: customToStandardPCC (PCS  PCS) Defines a transform that converts the from the custom viewing condition colorimetry to standard viewing condition colorimetry. standardToCustomPCC (PCS  PCS) Defines a transform that converts the from standard viewing condition colorimetry to the custom viewing condition. Or use CMM default methods, maybe an appearance model.

Changing measurement standards Not everything that counts can be counted, and not everything that can be counted counts - Albert Einstein, (attributed)

The problem Example: The CIE defined two sets of color-matching functions for use as standard observers. CIE 1931 Standard Colorimetric. CIE 1964 Supplementary Standard Colorimetric. The difference is based on the field of view used in the collection of the experimental data. Which set of color-matching functions is more relevant for monitor calibration? Calibrating a color monitor involves measuring color patches that are displayed on the screen of the monitor. The patches are clearly larger than a 4-degree field of view. ICC Previous specs requires standard observer of 2º field of view

Profile Connection Conditions (PCC) Header color space and spectral PCS metadata measurementType records measurement conditions spectralViewingConditionsTag defines a structure that spectrally specifies observer and illuminant customToStandardPcsTag defines an MPE based tag to convert from custom PCS colorimetry to standard D50 / 2º observer colorimetry standardToCustomPcsTag defines an MPE based tag to convert from standard D50 / 2º observer colorimetry to custom PCS colorimetry

Profile Connection Conditions (PCC) A Sensor Adjustment Transform (SAT) transforms sensor excitations to sensor excitations independent of reason or method A Chromatic Adaptation Transform (CAT) predicts sensor excitations of corresponding colors (based on adaptation of human observer) Predicts appearance constancy A Material Adjustment Transform (MAT) predicts sensor excitations of an object for an observer/illuminant based on sensor excitations of the same object for a different observer/illuminant Predicts material constancy CAT’s and MAT’s are both examples of SAT’s

Special connection spaces

Example: Gloss enhancer ink

HP DesignJet Z3200

Workflow The workflow should: connect GE channels from input to output profile in some cases, Default GE to zero in some cases (non glossy media) Default GE to full in other cases (glossy with a special setting)

Gloss Enhancer Workflow Input (embedded) profile Output profile (for Glossy) PCS (Lab) GE channel to include ink-limit GE channel PCS (Lab) PCS (Lab) GE channel PCS (Lab)

Material Connection Spaces (MCS) A separate connection space defined by material channel identification for AToM0/MToA0/MToB0/MToS0 tags using a MCS signature field in the profile header. If this field is zero then material connection is not defined. MCS connection is performed by passing values for material channels between profiles that have identical Material Channel Type values (defined in the materialTypeArrayTag of both profiles). The MCS subset requirements must be met before profiles can be linked. Once these requirements are met the channels with a material type in the source profile that are not in the destination profile are ignored, and channels with material types in the destination profile that are not in the source profile are processed with the material value defined for the channel in the materialDefaultValuesTag or zero if this tag is not present.

Spectral matching

The problem Packaging printing Unexpected illuminants Different printers / batchs All placed together, side-by-side

General Colorimetric PCS Processing Convert to XYZ colorimetry Convert Spectral to XYZ colorimetry (using PCC) Convert from Lab to XYZ XYZ scaling for relative/absolute/BPC Conversion of PCS colorimetry (using PCC) Use source PCC customToStandardPcsTag Use destination PCC standardToCustomPcsTag Conversion to Lab (as needed)

Spectral PCS processing To define the use of a spectrally based PCS, one of the spectral colour space signatures in Table 17 shall be used to encode the colour space implied by the spectralPCS field of the profile header. These colour space signatures define both the colour space type as well as the number of channels associated with the colour space. Therefore, the number of channels implied by the spectralPCS colour space signature shall match the number of channels indicated by the steps field(s) of the corresponding spectralRange structures in the profile header. Spectral colour space type None (PCS defined by PCS header field) Reflectance spectra with N channels Transmission spectra with N channels Radiant (Emission) spectra with N channels Bi-spectral Reflectance spectra with N total channels Bi-spectral Reflectance using sparse matrix with N equivalent output channels

PCS Connection Support From Lab From XYZ From Reflectance From Transmissive From Radiant/ Emission From Fluorescence To Lab Yes Using PCC To XYZ To Reflectance No Extract PCC illuminant Apply then extract PCC illuminant To Transmissive Use PCC illuminant To Radiant / Emission Apply PCC Illuminant Apply PCC illuminant To Fluorescence Exact match

Fluorescence

The problem

The problem

Bi-Spectral Bispectral spectrophotometric instruments can make colorimetric measurements taking into account the contribution of both the fluorescent and the reflected component to the total radiance of a sample. This way the measurement becomes light-source independent and the full bispectral radiance factor can be obtained in a matrix form as a function of the excited wavelengths.

Bi-Spectral

Wrap-Up

Taming unusual workflows with iccMAX Changing viewing conditions  PCC Changes in measurement standards  PCC Special connection spaces  MCS Spectral matching  Spectral PCS. Fluorescence  Bi-Spectral PCS

Taming unusual workflows with iccMAX Thank you! Taming unusual workflows with iccMAX