1. Working together toward greater efficiency
Practical Evaluation of
Spectrophotometers for Color
Management Purposes
Fons Put
VIGC - 26/05/2009

2. Introduction
• Flemish Innovationcenter for Graphic
Communication
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 2

3. Introduction
• Do we understand the printing proces?
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 3

4. Introduction
• Do we understand the printing proces ?
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions Original Reproductions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 4

5. Introduction
• Process control
• ISO standards (TC130)
• ISO 12647-2 (Print)
• ISO 12647-7 (Proof)
• ISO 3664 (Visual comparison Print-Proof)
• Measurement strips
• Print certification
• Proof validation
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 5

6. Introduction
• Process control
• Measurement Reports
• ISO 12647-2 (Print)
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 6

7. Color Measuring

8. Color Measuring
• What can be measured in the printing
process?
• The intensity of radiated light
• Unit: The CANDELA
• Derivatives: Density, CIELab, brightness,…
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 8

9. Color Measuring
• Color measuring devices
• Concept
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 9

10. Color Measuring
• Color measuring devices
• Distinctions: Light Source
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 10

11. Color Measuring
• Color measuring devices
• D50 light (theoretical)
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 11

12. Color Measuring
• Color measuring devices
• Gas Filled Tungsten (mostly used)
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
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13. Color Measuring
• Color measuring devices
• White LED (recent)
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
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14. Color Measuring
• Color measuring devices
• Other Distinctions: Scanning Interval
• Reflective measurements: 10nm interval
• Lightsource measurements: 5nm interval
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 14

15. Color Measuring
• Color measuring devices
• Scanning Interval: examples
• Reflective measurements: cyan procescolor
• Lightsource measurements: fluorescent light
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 15

16. Color Measuring
• Color measuring devices
• Other Distinctions: Bandwidth
• Minimum requirement 400/700 nm
• Best: 340/780 nm
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 16

17. Color Measuring
• Color measuring devices
• Other Distinctions: Geometry
• 45°/0° or O°/45° for reflective measurements
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 17

18. Color Measuring
• Elements of a color measurement
• Measurement Result
• Spectral power distribution
• CIELAB
• Density
• Tolerance (examples)
• 0.3 ΔE* CIELAB
• 0.15 ΔE CMC(2:1)
• Average DE*94 0.4
• Reliability
Contents
• Do circumstances allow reliable measurements?
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 18

19. Color Measuring
• Elements of a color measurement
• Reliability
• Example
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 19

20. Spectrophotometers

21. Spectrophotometers
• Starting point
• Practical Research
• Performance within the company, not in lab.
• Scope
• 6 different types
• Total of 20 measurement devices
• Test-setup
• Repeatability
• General Accuracy
• Detailed Accuracy
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 21

22. Spectrophotometers
• Repeatability
• Can the instrument repeat the measurement
with sufficient accuracy?
• Procedure
• 12 consecutive measurement of a white and blue
patch.
• Same spot (no disposition of the instrument)
• Calculation of the average CIELAB color of the 12
measurement
• Calculation of the average color difference ΔE*ab
Contents of the 12 measurement with the average color
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 22

23. Spectrophotometers
• Repeatability
• Results (white patch)
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 23

24. Spectrophotometers
• Repeatability
• Results (blue patch)
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 24

25. Spectrophotometers
• Accuracy (general)
• Can the instrument measure color
accurately?
• Procedure
• measurement of 13 different colors of a
Netprofiler color chart.
• Calculation of the average CIELAB color of the 13
measured colors
• Calculation of the color difference ΔE*ab of the 13
measurement with the reference of the Netprofiler
chart.
Contents
• Averaging of the 13 calculated ΔE*ab-values.
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 25

26. Spectrophotometers
• Accuracy
• Results
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 26

27. Spectrophotometers
• Accuracy (detail)
• Which colors can the instrument measure
accurately?
• Procedure
• measurement of 13 different colors of a
Netprofiler color chart.
• Calculation of the average CIELAB color of the 13
measured colors
• Calculation of the color difference ΔE*ab of the 13
measurement with the reference of the Netprofiler
chart.
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 27

28. Spectrophotometers
• Accuracy
• Results
• Average of all instruments
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 28

29. Spectrophotometers
• Accuracy
• Results
• According to Instrument type
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 29

30. Spectrophotometers
• Accuracy
• Results
• According to Instrument Brand
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 30

31. Spectrophotometers
• Accuracy
• Results
• According to Instrument age
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 31

32. Spectrophotometers
• Accuracy
• Results
• According to Instrument maintenance
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 32

33. Conclusions

34. Conclusions
• Technological evolution
• Search for more suitable light sources is ongoing
• Instrument Type
• Don’r rely on older instrument types for accurate
measurements
• Instrument Brand
• Different brands show different behaviour
• Instrument Maintenance
• Maintenance (white kalibration patch) is very
Contents important.
• Introduction
• Color Measuring • Averaging
• Spectrophotometers • Make use of sufficient averaged measurements to
• Conclusions judge color.
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 34

35. Future Work
• Expansion toward measurement tables
in press rooms
• Example: color accuracy
Contents
• Introduction
• Color Measuring
• Spectrophotometers
• Conclusions
© VIGC - 7/09/2009 Practical Evaluation of Spectrophotometers for Color Management Purposes 35

36. Thanks :-)

37. Titel seminarie
Working together toward greater efficiency

38. Strategic partners VIGC