Oce VarioPrint i Series, Operation Manual

Page: 379 / 402

Creation of calibration curves
The illustrations below explain how the calibration curves are created. (
Learn about media family
calibration on page 234
)
1. Imagine, you use an i1 spectrophotometer to measure a test chart with magenta gradients
from 0% to 100%. The measured Lab values will compose a straight line from white (Lab
0,0,0) to the lab colour value at 100%.
0%
Lab value
100%
(0,0,0)
2. A Lab value is a three-dimensional value that does not allow for easy colour comparisons. It
helps when a colour value on this line could be expressed as a single value, such as the (∆E)
metric to express a colour difference.
A value based on a colour difference can be created as follows. The difference between the
Lab value of a colour and the Lab value of paper white (0,0,0) delivers a ∆E value. (
Learn
about colour differences on page 261 )
The maximum colour value (expressed in ∆E) refers to the 100% tone value.
0%
∆E
100%
(0,0,0)
Max
3. When you perform a media family calibration, all measured values of the patches are
compared with the values expected from the output profile. PRISMAsync Print Server
calculates for every patch a correction value. The results are extrapolated to gradients that
have not been measured. In this example, patch 1 represents the 5% tone value and patch 5
the 100% tone value.
Creation of calibration curves
Chapter 14 - References 379