EXact X-Rite User's Guide download pdf (Page 41)

X-Rite eXact™ Instrument

Hue Error and Grayness Function

Hue Error indicates the variation of a printed color from a theoretical pure color. Grayness

indicates the presence of gray in a color that makes it appear less saturated. Hue Error and

Grayness are used to check for color consistency throughout a press run.

Hue error and grayness are calculated using the following formulas.

100x

−

100x

Where: D

= Highest density of C, M, or Y.

= 2nd highest density of C, M, or Y.

= Lowest density of C, M, or Y.

Hue Error and Grayness Measurement

Displays hue error and grayness with or without paper subtracted. Hue/Gray measures the

selected ink through all three filters (cyan, magenta, and yellow). Hue error and grayness values

are displayed along with color toward color: V (visual), C (cyan), M (magenta), and Y (yellow).

For example, C -> Y indicates the color is cyan toward yellow.

1. Select Hue Error & Grayness function.

2. Measure paper if required.

3. Measure solid patch.

4. View data.

Colormetric Functions

CIE L*a*b*

This function is derived from the CIE 1931 XYZ color space in an effort to be perceptually uniform.

The L* dimension related to Lightness while a*(red/green) and b* (yellow/blue) are for color.

Perceptually uniform means that a change of the same amount in a color value should produce a

change of about the same visual importance. When a valid standard is present, the delta values

will be included along with the delta E type that is configured.

CIE L*C*h°

This function is a colorspace equivalent to CIEL*a*b*, the main difference is that in L*a*b* the

color values are plotted in a Cartesian coordinate system, while L*C*h° is polar coordinate

system. L* stays the same, but C* refers to chroma or strength which is the radius and h° is the

hue angle. When a valid standard is present, the delta values will be included along with the delta

E type that is configured.

Simulated color and timestamp of

reading displayed

Function, response, and

Measurement Condition selected

Hue error and grayness

values

Cyan towards Magenta

1 2 ... 36 37 38 39 40 41 42 43 44 45 46 ... 103 104

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EXact X-Rite User's Guide Page 41