Color iQC Help - X-Rite

The center box, within which the standard falls, is designated the 555 box,
and any other samples which fall into this box are judged to be equal to the
standard and given the same sort code of 555.
As samples fall further away from the standard in any direction, they will
fall into other boxes and be accordingly classified. Thus, you can instantly relate
the fact that five rolls which are each coded 375 are darker and brighter that the
standard, but sufficiently close to one another to be used in the same garment.
This ability of sort code numbers to convey useful information about each
sample's relationship not only to the standard but to other samples makes it a
successful method for minimizing the problems associated with shade variation.
How close the samples all falling into one sort block are to each other
depends on the size of that sort block. In Color iControl, you have the choice to
select from one to nine as the sort block range, with the most common choice
being five (this is also the default range).
A sort block setting of five means that there will be two levels of sort
blocks (within the tolerances) calculated above the central block level containing
the 555 block and two below, setting the range to seven means that there will be
three levels of sort blocks above and below the one containing the 555 block.
However, no matter how many or how few sort blocks you choose, they
will be dividing up the same ellipsoid of acceptability. Therefore, the greater the
sort block range, the smaller each block will be and the closer each sample in
that block will be in shade to each other.
So, we must understand what are the factors that determine the ellipsoid
of acceptability.
Factors Determining the Ellipsoid of Acceptability
There are three factors which determine the size of the ellipsoid of
acceptability which Color iControl draws around the standard and which is
divided up to form the 555 shade sorting blocks (when using DEcmc to
calculate).
These three factors are the L*a*b* values for the standard, the pass/fail
volume, and the l:c ratio. The L*a*b* values determine the standard's location in
color space. This is very important since color space is not uniform. The ellipse
for a yellow sample will be larger than the ellipse for a blue sample even if the
three factors are set to the same values due to the differences in the yellow
portion of color space as opposed to the blue.
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