ColorImaging.tioga
Maureen Stone, July 19, 1987 10:24:39 pm PDT
Digital halftones
Contouring ?
figure from stanford talk
Pair of idealized spectra
Pair of real spectra (?)
More PrintervsMonitor
process diagram
New GamutMapping based on TOG picture?
Color Imaging and Reproduction
Color Production
Color Reproduction
Same Image
Different Device
Color Measurement
CIE Colorimetry
CIE Color Standards
Calibrated Color Reproduction
What is Color?
Red, Green, Yellow, ...
Hue, Tone, Tint ...
Response of Eye to Stimulus
Perception of Stimulus
Anything not a Mask
Color Devices
Additive (Monitors)
Subtractive (Printers, photograpy)
Device Primaries
RGB, CMY(K)
Bilevel or Multilevel
Color Monitors
Three Phosphor Dots/Pixel (Picture of single pixel)
Full Color (8 bits/color) (Picture of pixels 24bpp)
Color Lookup Tables (8 bits/pixel) (Picture of pixels 8 bpp)
Primaries are Pure
50% R+50% G + 50% B = 50% gray
Gamma Correction
Linear in Intensity
Color Printing
Three or Four Colors
Halftones
Bilevel
50 to 170 lines/inch
Primaries are not Pure
50% C+50% M + 50% Y NOT = 50% gray
Gray Balancing
Linear in Density
BW halftones
Color halftones
Classic Separation, Black-printer Sequence
Digital Color Printing
Bilevel Technologies
Inkjet
Electrostatic
Xerography, Electrophotography
Thermal Transfer
Offset Printing
Multilevel Technologies
Photographic Processes
Thermal Sublimation
Digital Halftones
Multiple Printer Pixels/Halftone Dot
Gray Levels vs. Sharp Edges
10:1 typical
10 by 10 = 101 gray levels
150 lines = 1500 spi
Typical Resolutions: 150 to 400 spi
Poor Resolution, but good Alignment
Digital halftones
Contouring
Color Reproduction
Same Image
Different Output Devices
Same Appearance
Graphic Arts Rules-of-Thumb
Customer Satisfaction
Color Names don't Change
Gray Wedge is Smooth and Gray
Good Contrast
Designing on Monitors for Printers
Additive vs Subtractive Color
Different Viewing Environments
User Model
Functional Color
Select Percentage CMYK
RGB to CMY(K) automatically
RGB to CMY(K)
If Inks were Ideal Filters
C = 1-R, M = 1-G, Y = 1-B
Inks are not Ideal Filters
Spectra Overlap
Not Inverse of Monitor Spectra
Color Correction Required
figure from stanford talk
Pair of idealized spectra
Pair of real spectra (?)
Color Correction
Map Input to Output Colors
Compensate
For Impurity
For Color of Primaries
Different Gamuts
Techniques
Simple Linear Transformation
Piecewise Interpolation
Mik's sequence
Color Measurement
What is Color?
Colorimetry
Instruments Measure the Stimulus
Empirically Derived
Metrics Standardized by the CIE
What is color measurement
Diagrammed image from colorimetry
Radiometer with Spectrum showing
TV Color Analyzer
Mik's colorimeter
Device Calibration
Define Device Properties in Colorimetric Terms
Model
Measure
Gamut is the Set of all Possible Colors
PrintervsMonitor
PrinterGamuts
MonitorGamuts
Introduction to Colorimetry (7)
CIEColorimetry
CIEStandards
TristimulusValues
tristimulusEqns
ChromaticityEqns
CDAdditive
Printer vs Monitor
Calibrated Color Reproduction
Color Correction based on Colorimetric Information
Calibrated Devices
Possible Reproduction Levels
Match Surfaces
Match Tristimulus Values
Match Chromaticity Coordinates
Match Appearance
AIC Experiment (show some examples)
Bits to Color Separations
Different images with different problems
3 slides (tape, seps, cromalin)
process diagram
Gamut Mapping
Appearance Match is the Correct Goal
Map to Control Appearance
Map to Control Out-of-Gamut Colors
Don't Match Tristimulus Values
Don't Match Chromaticity Coordinates
Conclusions
Increasing Number of Digital Color Devices
Many are Poor Quality
Many are Badly Used
Color Reproduction Important Issue
  for Computer Graphics Community
Scholarly Publishing
Desktop Publishing
Community needs to be Educated
Color Measurement Key to Quality Reproduction