BAM Federal Institute for Materials Research and Testing
Prof. Dr. Klaus
contact point :
+49 30 8104-1917
|Visual Methods and Image Reproduction|
|Image reproduction linearisation|
Image reproduction linearisation of 16 step colour scales, see Technical Report ISO/IEC TR 19797:2004
Standards, short title and information about standard test
Linearisation method for the reproduction
The linearisation method is described for black and white printers and used by students in a competition of colour science during the international colour meeting FARB-INFO '02, see info02/FI02WE.PDF
Linearization data for a reproduction process
For an example linearisation file with linearisation data to be used at the four above places, see info02/MTL20000.PS. This file includes PostScript code of about 50 lines with different relative visual data (linear, square root and square) and colorimetric CIELAB lightness data L* of a start output of a printer. The last data may be changed according to the start output of the device system used.
In the recommended file for the start output the digital data 0, 1/15, 2/15, ..., 14/15, 1 are equally spaced for the top grey series. According to the standards the output should also appear equally spaced. The four 16 step gray series appear differently spaced and this is based on the different input data used. The exponents 1/2, 1,5 and 2,0 for the data 0, 1/15, ..., 14/15, 1 are used for the three lower grey scales (see figure description)
In the top series often less than 16 steps can be recognized and the steps appear not equally spaced. It is recommended to measure the output of the top 16 step grey colours. If the lightness L* data in the file info02/MTL20000.PS are exchanged then an equally spaced output in CIELAB lightness L* will be produced for the top grey series. If any other series is measured and the output L* lightness data are exchanged then this series will be equally spaced in the second output.
If the linearisation method is used, then the output of the test file is in most cases independent of the the application software, the printer driver and the device.
Therefore it is useful to store the colorimetric measurement data of a reproduction process in the Distiller startup directory and to produce PDF files from PS files, e. g. by the software Adobe Acrobat Distiller. Every PDF file will then produce a linearized output on any corresponding (measured) printer or monitor (not only on PS devices). In the office area then the colour output is very similar for the different device systems.
Problem of different output if different PS operators and with CIELAB corresponding colour data are used.
Requirement for a similar output by the consumers
Solution with the Measurement, Transfer and Linearisation
Training of the image programming language PostScript (PS)
DIN 33870: Start and linearized printer output
Test files and multistep output linearization
DE04: 001222: Test material: digital 16 step test charts as basis for linearising 16 step black and white and colour series
DE05: 010105: Test material: digital 16 step test charts - Linearising 16 step output of different file formats PS, PDF, BMP, GIF, TIF, etc.
Start and linearized printer output
DE09: 010301: Start and linearized printer output of the achromatic ISO/IEC-test chart no. 3 according to ISO/IEC 15775:1999-12
DE10: 010415: Start and linearized printer output of the chromatic ISO/IEC-test chart no. 2 according to ISO/IEC 15775:1999-12
DE11: 010415 Start and linearized printer output of the chromatic ISO/IEC-test chart no. 4 according to ISO/IEC 15775:1999-12
Test material for linearization of colour image reproduction