Digital color assessment

An apparatus, comprising:

• an enclosure defining a principle axis;
• a lens coupled to the enclosure, the lens defining an optic axis that substantially parallel to the principle axis of the enclosure;
• a camera coupled to the lens;
• an image processing circuit coupled to the camera;
• and
• a plurality of elongated light sources defining a plurality of illuminant axes located substantially symmetrically around the principle axis of the enclosure,
• wherein the each of the plurality of elongated light sources includes a plurality of independently controllable segments.

A method of making a wide gamut color chart, comprising:

• providing a substrate;
• laying out a pattern for color patches on a surface of the substrate to define a total number of available color patches;
• allocating a first fraction of the total number of available color patches to a set of boundary colors;
• allocating a second fraction of the total number of available color patches to a set of interior colors;
• picking the set of boundary colors by substantially randomly sampling the set of boundary colors from an outer surface of a gamut of all colors that are producible with regard to a color production machine;
• writing the set of boundary colors to a digital file;
• dividing the gamut of all printable colors into a plurality of substantially equal sub-volumes corresponding to the second fraction of the total number of available color patches;
• picking the set of interior colors by sampling an interior color from an interior of each of the plurality of substantially equal sub-volumes;
• writing the set of interior colors to the digital file;
• converting the digital file to a native color space of the color production machine;
• producing a set of boundary color patches corresponding to the first fraction of the total number of available color patches on the surface of the substrate using the color production machine;
• and
• producing a set of interior color patches corresponding to the second fraction of the total number of available color patches on the surface of the substrate using the color production machine.

A manufacture, comprising:

• a wide gamut color chart including
• a substrate and
• a plurality of color patches coupled to the substrate,
• wherein a first fraction of the plurality of color patches are boundary colors selected from a boundary of a wide gamut and
• wherein a second fraction of the plurality of color patches are interior colors selected from each of a plurality of substantially equal sub-volumes defined within the wide gamut.

A method of making a custom color calibration chart, comprising:

• measuring spectroscopically a plurality of sample areas on a workpiece and a plurality of color patches on a wide gamut color chart under substantially identical lighting conditions;
• writing data representing the measured plurality of sample areas and the measured plurality of color patches to a digital file;
• computing L*a*b* values from the measured plurality of sample areas and the measured plurality of color patches;
• writing the computed L*a*b* values to the digital file;
• providing a substrate;
• laying out a pattern for color patches on a surface of the substrate to define a total number of available color patches;
• allocating a first fraction of the total number of available color patches to a set of boundary colors selected from boundary colors that are present on the wide gamut color chart;
• allocating a second fraction of the total number of available color patches to a set of sample gamut colors selected from interior colors that are present on the wide gamut color chart;
• picking the set of boundary colors from boundary colors that are present on the wide gamut color chart based at least some of the set of boundary colors being close to computed L*a*b* values from the measured plurality of sample areas;
• writing the set of boundary colors to a digital file;
• picking the set of sample gamut colors from interior colors that are present on the wide gamut color chart based on closest available to computed L*a*b* values from the measured plurality of sample areas;
• writing the set of sample gamut colors to the digital file;
• converting the digital file to a native color space of the color production machine;
• producing a set of boundary color patches corresponding to the first fraction of the total number of available color patches on the surface of the substrate using the color production machine;
• and
• producing a set of sample gamut color patches corresponding to the second fraction of the total number of available color patches on the surface of the substrate using the color production machine.

A manufacture comprising:

• a custom color calibration chart including
• a substrate;
• and
• a plurality of color patches coupled to the substrate
• wherein a first fraction of the plurality of color patches are boundary colors selected from a boundary of a wide gamut and
• wherein a second fraction of the plurality of color patches are sample gamut colors selected from each of a plurality of substantially equal sub-volumes within a gamut of interest defined by a digitally imaged workpiece.