1. 4. All About Profiles
5. Measurement, Calibration, and Process Control 6. Building Display Profiles
GED119 Colour Science and Digital Applications

2. What are Device Profiles
A profile is just a “table” correlating device colour values (e.g. RGB numbers) with device-independent colour values (LAB numbers).
Conceptually:
RGB numbers:
255, 255, 255
255, 255, 254
255, 255, 253 …
0, 0, 1
0, 0, 0
LAB numbers:
92,0,0
92,0,1
91,0,2
3,1,2
3,1,0
GED119 Colour Science and Digital Applications

3. Profiles

4. Profiles Classes
One-way input profile
Two-way display/output profile

5. One-way Input Profiles
An input profile matches an input device colours to LAB (one-way)
RGB numbers:
255, 255, 255
255, 255, 254
255, 255, 253 …
0, 0, 1
0, 0, 0
LAB numbers:
92,0,0
92,0,1
91,0,2
3,1,2
3,1,0
RGB numbers:
255, 255, 255
255, 255, 254
255, 255, 253 …
0, 0, 1
0, 0, 0
LAB numbers:
93,0,1
93,1,1
90,1,2
4,1,3
3,2,0

6. Two-way Display Profiles
A display profile is two-way:
LAB colours must be matched to device’s RGB numbers for display (output)
Colours according to RGB numbers must be matched to LAB (input)
RGB numbers:
255, 255, 255
255, 255, 254
255, 255, 253 …
0, 0, 1
0, 0, 0
LAB numbers:
99,99,99
99,99,98
92,0,0
92,0,1
92,0,2
91,0,2
3,1,2
3,1,0
3,0,1
Out-of-gamut

7. Two-way Output Profiles
An output profile is also two-way:
LAB colours must be matched to device’s RGB/CMYK numbers for output
Colours printed according to RGB/CMYK numbers must be matched to LAB for display/proofing on other devices
CMYK numbers:
0,0,0,0
1,0,0,0
1,0,0,1 …
89,69,69,69
90,70,70,70
LAB numbers:
99,99,99
99,99,98
92,0,0
92,0,1
92,0,2
91,0,2
3,1,2
3,1,0
3,0,1
Out-of-gamut
LAB numbers:
92,0,0
92,0,1
91,0,2 …
3,1,2
3,1,0

8. Making Profiles
For a display device such as a monitor, send RGB values (signals) to the screen and measure exactly what colours in LAB come out on the display (screen).
For an output device such as a printer, send RGB /CMYK values (signals) to the device and measure exactly what colours in LAB come out on the output medium (e.g. paper).

9. Making Profiles
For an input device such as a scanner or a digital camera, a scanning target with pre-measured LAB values are used. The input device scans the target and produces an RGB file which has to be correlated with the pre-measured LAB values of the target.

10. Profile Limitations
The profile maker cannot measure all possible device (colour) signals.
A profile can address only those colours within the gamut of a device.
A profile is only as accurate as the measurements from which it is made.

11. Calibration vs. Profiling
Calibration is the act of changing a device’s behaviour to achieve some desired state.
Profiling is the process by which we record a device’s behaviour into a profile. It does not change the device’s behaviour.
Some devices do not support calibration because they cannot be adjusted, e.g. desktop scanners.
GED119 Colour Science and Digital Applications

12. Controlling Variables
Devices have their internal software (firmware) which control their colour behaviour, e.g. auto colour correction in printers.
Printer profiles are dependent on inks and papers. Be careful of manufacturing variations/changes in these consumables.
For devices with hardware settings, be careful of keeping them constant.

13. Calibrating Devices
Aim: adjusting a device so that it always produces the same colour in response to a given set of (RGB/CMYK) numbers.
Other goals:
Stability – when devices change their behaviour over time.
Optimization – exploit the full dynamic range and colour gamut
Simulation – adjust a device to behave like another device, e.g. soft proofing

14. Building Display Profiles
What to adjust:
Monitor control settings
Video Lookup Table (videoLUT)
Calibration and Profiling Tools
Packages bundled with a monitor
Standalone instrument-and-software bundles
Standalone software packages that support different instruments
Visual calibrators

15. Before Calibration Allow sufficient warm up time
Check monitor settings
Clean the screen

16. Demonstration Calibrate a notebook PC LCD screen
X-rite Colormunki Photo: a software-and-instrument package