The last details view displays the gray values.
Gray balance is not a set feature in the ISO standard but is a requirement in the GRACOL standard. However, the gray balance process standard check as a quality indicator for high-quality print products is also very useful in the "ISO environment".
Note: This check shows values only if you use a minispot to check the gray balance (see also 'ECI_GrayConL', 'ECI_GrayConM' and 'ECI_GrayConS' with 52, 32 or 6 Patches).
•GrayConL_...: This refers to the long version of the test strip with 52 patches. It is to be placed vertically, parallel to printing direction, and is especially suited for checking ink balance and any faults in gray balance.
•GrayConM_... (GrayConM_Eye1_...): This refers to the medium version of the test strip with 32 patches (there are less graduations in the primary colors). This strip should only be used if there is not enough room for the "L" version.
•GrayConS_...: This refers to the small version of the test strip with only six patches (three gray balance pairs). This test strip is designed only for a visual check.
In addition to checking the dot gain and the CIELab and density values, you can also check the gray balance with this evaluation.
The additional grays of the control strip (K30, K50, K70 and their corresponding chromatic grays in CMY) are evaluated for gray balance. The results display in a table and a graph.
The ISO 12647-2 process standard specifies that a gray composed of the three chromatic process colors has the same L*, a* and b* values (CIELab) as an identical gray that is printed only with black.
In this case, the L*, a* and b* values for three real grays (black only) are compared at 30%, 50% and 70% with those of the identical chromatic grays (cyan, magenta and yellow) and shown as a table and a diagram with the calculated differential values for chroma difference (ΔCh* (Ch* = chroma)) and lightness distance (ΔE):
•green if the deviations are within the tolerance range
•red if they are outside it.
Chroma (Ch*) describes the intensity of the difference in color. It describes what makes this color different from one which is perceived as achromatic and has the same degree of brightness. Terms such as gray, pastel-colored, very chromatic, etc. are used to describe this property. Chroma depends greatly on lightness. Colors perceived as being very light or very dark have only a slight amount of chroma.
Chroma difference ΔCh* describes color casts that are perceived much more in neutral gray areas of an image than in chromatic areas.
ΔCh* is the geometric distance between reference and target on the ab plane.
In the "Preferences", 'Individual Quality Index (IQI)' tab, in "Gray balance" you can define the tolerance for the gray balance check within the process standard check. The sampling points are "K30", "K50" and "K70".
The default value is 3.0. Values ranging between 3.0 and 4.0 make sense. The permissible values for the evaluations lie between 0 and 10.
Minispots for the evaluation of gray balance
Four variants of a new minispot are also available for the evaluation of the gray balance:
•PCM_GrayConL_i1_39: Paper grade 1 and 2, gloss coated and matt coated
•PCM_GrayConL_i1_43: FM screen, paper grade 1 and 2, gloss coated and matt coated
•PCM_GrayConL_i1_44: FM screen, paper grade 4, uncoated white
•PCM_GrayConL_i1_47: Paper grade 4, uncoated white
The advantages of these minispots are that there are 10 color patches for each color channel, in addition six color patches for the evaluation and calculation of the gray balance: K30, K50, K70 as well as CMY30, CMY50 and CMY70. You can measure these strips with the X-Rite EyeOne strip in two measure runs.