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How to interpret data – Variation Inspector

How to interpret data – Variation Inspector

 

 

1. ∆E Variation (Precision/Consistency) 

Example 1 – high precision device

On presented sample, we can see two measurement samples of VI-816 test form 
The device can reproduce color with extremely small variations (high precision/consistency). 

Substrate is very consistent – for 276 measured samples mean variation is 0.1 ∆E (which equals +/- 0.05 ∆E)


An Instrument Inspector E-Factor for the spectrophotometer is:

Measurement device repeatability is fairly precise! This information can be displayed on tracklist (dashboard)


In the given sample, all values are very small

Graphs below show statistical distribution – vertical – number of samples, horizontal – ∆E
One single bar shows that all samples have a minimal error.



Cyan and Yellow are perfect, Magenta almost perfect with some small issues with Black. These graphs represent spectral values from more than 7000 pairs! Listed values show the ∆E between like values – not a distance from any target aim. That means that the target will be in a very center – and other values will be half of current result!

 


Variation for Red reflects small issues in Magenta, Green is perfect, we can see some minor problems in the Blue overprint.

 


 

CMY Grays are reproduced very consistently. Grays are the most volatile builds because they combine tints (dot gain) of C, M and Y components and can be accentuated due to all the variables that affect dot gain including ink-water balance, quality of water and potential slurring/doubling issues.
 

 

 

Example 2 – Low precision device

Below are the same set of graphics captured from measurements from an unstable (low precision) device/print condition. 45 measurement samples from a simple color bar (including substrate and CMYK solids) produced such Low Precision (inconsistent) results! 

 


In this case, the Black imaging unit works numerically better than the others.
There has to be a reason – probably due to a mechanical issue.Extremely high variation in gray builds can be reduced by using Alwan ColorHub – which replaces CMY builds with K only which greatly improves precision! 

 

Variation of tints

These are the detailed graphs for all recognized primaries tints
– but the most informative is a graph showing the error distribution: 


The worst results are in the Black, second worst is the Cyan.  If 95 percentile is less than 1 there is no big problem.

 

Example 2 – Extremly low precision device


In some cases, values can be extremely high:

This printing process is very unstable – could be operator induced, could be that the device requires maintenance!nIt could be due to very low quality, inconsistent substrate, or other consumables. Additional tests are required to pinpoint the problem. 

In offset, precision problems come from slurring/doubling issues (movement in the device), we recommend steps such as printing the ChromaChecker Slurring/Doubling test and check Nips of the Ink Rollers and the Cylinder pressures (with Nip Control Tools). For Ink-Jets it can be a printing head or a transport timing issues
 

 

 

2. ∆E Deviation (Accuracy)

 In the second part, there is an analysis of deviation calculated to Target Printing Aim (ICC Profile)

 

Here a device with high precision is not printing accurate – Cyan and Black are far away from aim value (11 and 8 delta E respective). To track the problem go to Print Inspector module for more detailed information.

Grays builds are NOT correct. Alwan ColorHub with high black generation setting can significantly reduce the problem, but the Black unit has to print correctly.

 

 

  

3. Density Range

This section shows the range of optical density – Operators can easier understand such numbers