1. Ph.D. Course in Digital Halftoning
Examples of Colorimetric Modeling Methods
Lars Bergman, Halmstad University

2. Digital halftoning - Lars Bergman
Papers
A Critical Review of Spectral Models Applied to Binary Color Printing
The Spectral Modeling of Large Format InkJet Printers
Digital halftoning - Lars Bergman

3. Digital halftoning - Lars Bergman
Forward
RGB -> CMY(K)
Reversed
How much CMY(K) for a given RGB
Predict the spectral output of the printer
Effective dot area
Digital halftoning - Lars Bergman

4. Digital halftoning - Lars Bergman
Effective dot area
Mechanical dot gain
Ink cover larger area on paper then intended
Optical dot gain
Light spread in paper (and ink)
Digital halftoning - Lars Bergman

5. Digital halftoning - Lars Bergman
Typical machanical dot gain for a desktop inkjet printer
Digital halftoning - Lars Bergman

6. A Critical Review of Spectral Models Applied to Binary Color Printing

7. Digital halftoning - Lars Bergman
Models
Regression based
Murray-Davis
Neugebauer
Yule-Nielsen
Yule-Nielsen modified Neugebauer
Cellular Neugebauer
Yule-Nielsen with spectral depending N-value
First principals models
(Regressing the Neugebauer Primarys)
(Expanded Murray-Davis Model)
The Propability model
Modeling paper spread function
Digital halftoning - Lars Bergman

8. Digital halftoning - Lars Bergman
Murray-Davis
Digital halftoning - Lars Bergman

9. Digital halftoning - Lars Bergman
effective area
Digital halftoning - Lars Bergman

10. Digital halftoning - Lars Bergman
Neugebauer
Digital halftoning - Lars Bergman

11. Digital halftoning - Lars Bergman
Digital halftoning - Lars Bergman

12. Digital halftoning - Lars Bergman
Yule-Nielsen
Trys to correct for the non linearity in Murray-Davis model
Recomended N=1.7 for offset prints
Digital halftoning - Lars Bergman

13. Digital halftoning - Lars Bergman
Digital halftoning - Lars Bergman

14. Yule-Nielsen modified Neugebauer
Combining Yule-Nielsen and Neugebauer
Yule-Nielsen is used separate for each color
Digital halftoning - Lars Bergman

15. Digital halftoning - Lars Bergman
Cellular Neugebauer
Digital halftoning - Lars Bergman

16. Yule-Nielsen with spectral depending N-value
Spectral reflectance for primary cyan ramp
Digital halftoning - Lars Bergman

17. Digital halftoning - Lars Bergman
The Propability model
Light path Probabilities
Digital halftoning - Lars Bergman

18. Digital halftoning - Lars Bergman
Digital halftoning - Lars Bergman

19. Modeling paper spread function
Convolution with LP filter
Can handle nonuniform screens/dots
Computational heavy
Digital halftoning - Lars Bergman

20. Digital halftoning - Lars Bergman
Quality meassure
Spectral fitness
RMS Spectral error
Tristimulus fitness
Humanly correct
ICC profiles
CIE DE
Digital halftoning - Lars Bergman

21. Digital halftoning - Lars Bergman
Model performances
Digital halftoning - Lars Bergman

22. The Spectral Modeling of Large Format InkJet Printers

23. Digital halftoning - Lars Bergman
Screening
Determing the number of colors (ink combinations)
Digital halftoning - Lars Bergman

24. Digital halftoning - Lars Bergman
HP650C
HP650 use ”Scatter mode” FM-based screening
Digital halftoning - Lars Bergman

25. Digital halftoning - Lars Bergman
Testdata
Primary ramp
CMYRGBK Ramp
Test target used to characterize each color types spectral absorptivity.
Digital halftoning - Lars Bergman

26. Digital halftoning - Lars Bergman
Meassured spectral rflectance factor data of a cyan ramp
Digital halftoning - Lars Bergman

27. Digital halftoning - Lars Bergman
Linear model prediction for 50% cyan using Murray-Davis model
Digital halftoning - Lars Bergman

28. Digital halftoning - Lars Bergman
Normalized reflectance factor spectra for cyan ramp data
Digital halftoning - Lars Bergman

29. Digital halftoning - Lars Bergman
Normalized reflectance factor spectra for cyan ramp data using Yule-Nielsen-model N=1.7
Digital halftoning - Lars Bergman

30. Digital halftoning - Lars Bergman
Normalized reflectance factor spectra for cyan ramp data using Yule-Nielsen-model N=10
Digital halftoning - Lars Bergman

31. Digital halftoning - Lars Bergman
Linear model prediction for 50% cyan
Digital halftoning - Lars Bergman

32. Digital halftoning - Lars Bergman
Normalized absorbtion spectra for cyan ramp data using Kubelka-Munck transparent model
Digital halftoning - Lars Bergman

33. Digital halftoning - Lars Bergman
Normalized absorptivities based on eigenvector analyses of eight possible
color types.
Digital halftoning - Lars Bergman

34. Digital halftoning - Lars Bergman
Method
Evaluate halftoning algorithm in order to determine the number of possible colortypes.
Hypothesize a color formation model
Evaluate how well the hypothesized model predict primary ramps
Evaluate secondary and tertiaries ramps
Quantify the mechanical dot gain
Digital halftoning - Lars Bergman

35. Digital halftoning - Lars Bergman
Experiments
Device driver
GCR
Registration
Test target design
Printer stability
Digital halftoning - Lars Bergman

36. Optimized Yule-Nielsen n value for CMYRGBK
Digital halftoning - Lars Bergman

37. The END