184212 and 030101: A/DE84/DE841.HTM
For the start page, see DE84 in English or DG84 in German.
For this page with MTL code for OL with:
CIEXYZ data of luminous colours, see
IE841 in English and IG841 in German,
CIELAB data of surface colours, see
DE841 in English and DG841 in German,
For additional Information, see
IE801 in English and IG801 in German,
DE801 in English and DG801 in German.
1.0 Colour Workflow (CF) for two different input and eight different output PS operators (device dependent and device independent).
Remark: The transfer of an input PS operator, which use e. g. relative cmyn* coordinates, to a different output PS operator, which use e. g. olv* (rgb*) coordinates, is a main part of the colour workflow.
It is intended to produce the same colour scales for corresponding colours defined colorimetry by CIELAB in 8 different corresponding colour spaces. The 16 step colour scales (Fig. B4 of ISO/IEC-test chart no. 2) are studied here to reach this goal.
Remark: One may study first the output of the 5 step grey scale (Fig. C2 of ISO/IEC-test chart no. 3) in DE80.
The corresponding colours are defined by a PostScript MTL code (Measurement, Transfer and Linearization) which can be stored at different places in the colour workflow, e. g. the file, the PS printer, the printer driver (PPD file) or the Adobe Distiller Startup directory, compare the technical paper BAMGREY.PDF (2300 kByte, 16 pages) and others, see XY91
Any PS file which use many input PS operators can be changed in the same direction as the following example files if the PS MTL code is stored at an appropriate place (see above).
Remark: It is possible to produce from any application or any PDF file a PS file. By the computer operating system a PS printer must be selected for the production of a PS file. For example the black and white Apple Laserwriter PS/640. Only a PPD file (PS Printer Description file) may be selected, in reality this printer must not be present. So it is possible at any computer operating system to produce PS files.
2.0 Colour Workflow (CW) and files for Fig. B4 to B7 of the ISO/IEC-test chart no. 2 with 16 step colour scales which are equally spaced in CIELAB, see DE84
Remark: The device dependent coordinates cmyn* (of standard offset printing according to ISO/IEC 15775) are transferred to device independent LAB* coordinates in the CIELAB colour space by the MTL code. For every device (different monitors and printers) there are equations which transfer from the device independent coordinates LAB* to the device dependent coordinates and vice versa. The colour difference accuracy is intended to be below 3 in CIELAB and therefore the device must be linearized in CIELAB. The linearization method is described later.
Remark: The files with the extension .DAT include the PostScript MTL code which is also included in the FP files and then used for the file output. The content of the 8 files with the extension .DAT is identical, only the value of one parameter i*ptrsc (=0 to 7) differs. This parameter selects the one output PS operator (see second column of Table 1 and around line 20 in the DAT and FP file).
It is useful to study the NP file L84E00NP. PDF and the two of the FP files, e. g. L84E00FP. PDF and L84E01FP. PDF to realize some basic problems in image technology.
Remark about the size of the files: The size of the NP.PS and NP.PDF files is about 130 kBytes, the size of the FP.PS and FP.PDF files is about 230 and 350 kBytes.The size of the following tiff files is about 250 kBytes.
The output of the two corresponding 16 step colour scales of the NP.PDF file shows differences on the monitor. The two PS input operators cmy0* setcmykcolor and 000n* setcmykcolor or olv* setrgbcolor and w* setgray give very different output with the software Adobe Reader 3.0 or later.
The two corresponding colour scales of every FP.PDF file (see Table 1 in DE84) agree in output but the eight L84E0iFP files (i=0,1,...,7) differ in output with the software Adobe Reader 3.0 or later.
L84R0NFP.tiff (250 kByte)
Fig. 1: Screen foto of the two files L84E00NP. PDF and L84E00FP. PDF which are both viewed by the software Adobe Reader 5.0 (label R=Reader in filename on Macintosh OS X 10.2).
Remark about the tiff format: In application the software Mac Preview (see later) is a part of the software Apple Quicktime which comes with Microsoft Explorer 5.0 and produces the image of the tiff format by the web browser Plug-In.
The two corresponding colour scales CMYN (according to CIELAB) are defined in the different colour spaces cmyn* (left in the NP file) and olv* (right in the NP file)
The two corresponding colour scales CMYN in the NP file output are different with different software, e. g. Acrobat Reader, Mac OS X Preview.
The two corresponding colour scales CMYN in the FP file output (right) are equal with different software, e. g. Acrobat Reader, Mac OS X Preview.
Therefore any imaging system depends at least on the input PS operators used (here two possibilities) and the colour workflow (transfer from the input PS operators to the output PS operators) used. The colour workflow is defined here by the transfer between two different input PS operators to one output PS operator 000n* setcmykcolor in the FP file.
Remark 1: The eight NP files of Table 1 have the same content and differ only by the name (and one PS parameter i*ptrsc=0 to 7 at the beginning which is not used in the NP file but used to select the PS output operator in the FP file). The colours are defined by two different input PS operators, see the figure descriptions in the output.
Remark 2: The two corresponding colour scales look the same in each FP file but the different FP files look different and show the same effect as the different colour scales in the NP files.
Remark 3: It is intended to produce the same colour scales for corresponding colours defined by CIELAB colorimetry in corresponding colour spaces.
It is useful to consider again the NP file, e. g. L84E00NP. PDF to realize some more basic problems in image technology.
L84RP0NP.tiff (250 kByte)
Fig. 2: Screen foto of the the same file L84E00NP. PDF which is viewed by the software Adobe Reader 5.0 (left, Label R) and Mac OS X Preview (right, label P in filename)
If one uses the following software:
Adobe Reader 3.0 to 5.0, Adobe Photoshop 5.0 or later
then the NP file shows very different output
for the scales CMYN and the landolt-rings on the monitor
if the input PS operators cmyn* setcmykcolor (left) and
olv* setrgbcolor (right) are used.
If one uses one of the following software:
MAC OS X Preview, Omniweb Web browser
then the NP file shows the same output for the scales
CMYN and the landolt-rings on the monitor if the input
PS operators cmyn* setcmykcolor (left) and olv* setrgbcolor
(right) are used.
According to CIELAB colorimetry for the corresponding coordinates in corresponding colour spaces the same output is expected. The software Adobe Reader is not in agreement with this basic requirement of colorimetry which is at the same time a basic user requirement. The equivalent software MAC OS X Preview agrees in this point with CIELAB colorimetry which is shown in Fig. 3.
L84P0NFP.tiff (250 kByte)
Fig. 3: Screen foto of the two files L84E00NP. PDF and L84E00FP. PDF which are both viewed by the software Mac Preview (label P=Preview in filename on Macintosh OS X 10.2). The different PS operators used in the NP file give the same output and the output of the FP file is the same compared to the NP file.
If one uses instead of the series CMYN the colour series OLVN then the situation is similar:
L85R0NFP.tiff (250 kByte)
Fig. 4: Screen foto of the two files L85E00NP. PDF and L85E00FP. PDF which are both viewed by the software Adobe Reader 5.0 (label R=Reader in filename on Macintosh OS X 10.2).
L85RP0NP.tiff (250 kByte)
Fig. 5: Screen foto of the same file L85E00NP. PDF which is viewed by the software Adobe Reader 5.0 (left, Label R) and Mac OS X Preview (right, label P in filename).
L85P0NFP.tiff (250 kByte)
Fig. 6: Screen foto of the two files L85E00NP. PDF and L84E00FP. PDF which are both viewed by the software Mac Preview (label P=Preview in filename on Macintosh OS X 10.2). The different PS operators used in the NP file give the same output and the output of the FP file is the same compared to the NP file.
Basic results:
1. There is software, e. g. Mac OS X 10 Preview, which
produces equal output for corresponding input PS operators
in different colour spaces, e. g. for the PS operators cmyn*
setcmykcolor and olv* setrgbcolor.
2. If one compares the intended equal spacing of the 16
coulour steps, e. g. by the Landolt-rings, then there are
large differences on the monitor between different software, e.
g. the software Adobe Reader 3.0 to 5.0 or Mac OS X
10 Preview.
3.0 Basic user requirements for image technology software
There are two basic user requirements
1. For the corresponding colours in different colour spaces the same output colours must be produced.
2. For 16 step colour scales with equal digital spacing in the file 16 step output colour scales which sre equally spaced in the CIELAB must be produced.
According to the first user requirement
the following PS operators mut produces the same output colour:
1. 0.0 0.0 0.0 0.5 setcmykcolor
2. 0.5 setgray
3. 0.5 0.5 0.5 0.0 setcmykcolor
4. 0.5 0.5 0.5 setrgbcolor
5. 0.5 0.0 0.0 setcolor (in relative CIELAB space)
6. 56.7 0.0 0.0 setcolor (in absolute CIELAB space, offset
range 18.0 to 95.4)
Similar the following three PS operators
must produce the same cyan colour
3. 0.5 0.0 0.0 0.0 setcmykcolor
4. 0.0 0.5 0.5 setrgbcolor
6. 56.7 0.0 0.0 setcolor (in absolute CIELAB space,
offset range 18.0 to 95.4)
The first basic user requirement is to produce the same grey or the same cyan blue at least for the above PS operators no. 3 and 4. The NP file shows very different output on the monitor by Adobe Reader 3.0 to 5.0. In the case of monitor differences still about 10% of the PS printers on the market show the same PDF output. For about 90% of the printers the large differences on the monitor remain in the output. Often additional differences between equal scales on the monitor appear on the printer.
Result ot the test of the first basic
user requirement
For the monitor and printer output e. g. the software Adobe
Reader is not in agreement with the first basic user requirement.
Many of the Display PostScript Systems (e. g. Silicon Graphics DPS and Photoshop, Compac VAX Decwrite, Mac OS X Server: application Yap) and many of the Display PDF systems are in agreement with the first basic user requirement.
Remark ot the test of the second
basic user requirement (compare
clause 5.0)
The second basic user requirement is violated by most of
the software. This requirement to produce a mean grey or
mean cyan blue which is visually (and in CIELAB lightness L*)
in the middle between the CIELAB data of white (L*w=95.4)
and black or cyan blue is often not addressed. Instead
of the relative whiteness w*=0.5 (which corresponds to
the lightness L*=56.7) or relative cyan blue c*=0.5
the different software on the market produce a relative whiteness
w* or relative cyan blue c* between 0.25 and 0.75.
The agreed tolerance range according to ISO/IEC 15775 is 0.47
to 0.53.
Remark: One of the reasons for the large differences are the different devices as source of the imaging data. The raw data of most scanners show a linear relationship as function of the luminance of the original, the raw data of a professional video camera are proportional to the square root of the luminance and the raw data of the slide or negative film transmission data are proportional to the log of the luminance. Software and users must therefore consider very carefully the source of the data and the complex properties of the devices and the device software.
4.0 Different solutions which are in agreement with the two basic user requirements
It is necessary to use at least a 16 step grey scale to include the second user requirement of a linear relationship between w* input and L* output coordinates. This linear relationship makes the system compatible to CIELAB. Similar linear relationships are intended for the six 16 step colour scales.
The possible solutions may be first studied with the 5 step instead of 16 step colour scales for six different input and six different output PS operators in DE80
4.1 Solution to get the same output independent of the colour space (PS operator) used
All FP files show the same output which is independent of the input PS operator used. Therefore one can select an appropriate output PS operator. This selection is device and software dependent. Two examples for the output of the file L84E00NP.PDF for monitors and printers are given:
On monitors and with:
1. e.g. the software Adobe Reader 3.0 to 5.0 it is not
appropriate to use the output PS operator no. 3 nnn0* setcmykcolor
because of the brown appearance of the mean grey colours.
One may select no. 4 which appears neutral.
2. e. g. the software Macintosh Preview one may select
any of the four (there is no brown colour output).
On PS printers with the software Adobe
Reader 3.0 to 5.0 and:
1. e.g. the PS laser printer Phaser 740 one may select
one of the first two which looks neutral. The last two
appear yellowish green.
3. e. g. the PS laser printer OKI 8e one may select no.
2 which is the only neutral and the other three look greenish
brown and different.
For the 16 step colour series the choise is more difficult and no recommendation is given here.
4.2 Solution to get an equally spaced output independent of the colour space (PS operator) used
One must measure the coordinates LAB* of the CIELAB colour space for the 16 step grey or colour scale output. Alternative the LAB* data may be determined visually. For this it is appropriate to use the reflective and transparent ISO/IEC-test charts as reference for the comparison for printers and monitors.
In a first step the 16 LAB* data of the start output must replace the corresponding 16 reference data in the file L84E00FP.PS at the beginning of the file. One must replace the appropriate LAB* data of the four 16 step colour series CW, MW, YW, and NW which are produced by the output. One must search for this replacement the corresponding LAB* data lines, labels and PS operators.
LAB* data line, label, data type, and PS operators
no. 000 to 047: CW or MW or
YW L cmy0* setcmykcolor
no. 048 to 063: N-W L 000n* setcmykcolor
no. 128 to 175: CW or MW or YW L olv* setrgbcolor
no. 176 to 191: N-W L w* setgray
The standard data type is L=Linear data for the files L84.., but for some special files Q84.. and S84.. which produce lighter or darker output the data type is Q=Quadratic data or S=Square root data (see clause 4.3).
Remark: Fig. B4 of the ISO/IEC-test chart no. 2 includes the CMY colours with the labels C=cyan blue, M=magenta red, Y=yellow, N=black, W=white.
Remark: Fig. C4 of the ISO/IEC-test chart no. 4 inludes the OLV colours with the labels O=orange red, L=leaf green, V=violet blue, N=A=black (produced by three colours), W=white.
no. 064 to 111: OW or LW or
VW L cmy0* setcmykcolor
no. 112 to 127: A-W L nnn0* setcmykcolor (A=all three
colours cmy*)
no. 192 to 239: OW or LW or VW L olv* setrgbcolor
no. 240 to 255: A-W L www* setrgbcolor (A=all three colours
olv*)
It is easy to find the appropriate LAB* data lines lines for the PS operators with any editor in the FP file. The new file may be saved with a new PS file name. The next steps are the transfer of the PS file to the PDF file and the linearized output. One can check if the new spacing is linear by the determination of the new LAB* output data.
In general the CIELAB colour difference is reduced by a factor 3 to 5, e. g. from 9 to 3 or 15 to 3. The value 3 is similar as the value for the intended tolerance and the accuracy of roproduction across a printer or screen page.
4.3 Four examples, one example solution and results
1. In the file S84E00FP.PS we have replaced for the CMY output the L=Linear LAB* data by S=Square root LAB* data. The output of the file S84E00FP.PDF looks much darker. This shows the effect and may be of some value if the start output is too light.
2. In the file Q84E00FP.PS we have replaced for the CMYoutput the L=Linear LAB* data by Q=Quadratic LAB* data. The output of the file Q84E00FP.PDF looks much lighter. This shows the effect and may be of some value if the start output is too dark.
3. In the file S85E00FP.PS we have replaced for the OLV output the L=Linear LAB* data by S=Square root LAB* data. The output of the file S85E00FP.PDF looks much darker. This shows the effect and may be of some value if the start output is too light.
4. In the file Q85E00FP.PS we have replaced for the OLV output the L=Linear LAB* data by Q=Quadratic LAB* data. The output of the file Q85E00FP.PDF looks much lighter. This shows the effect and may be of some value if the start output is too dark.
It is intended to use the change of the scaling for any PS file. It is intended not to change the (standard) PS file by an additional PS code or additonal data. One solution is to produce a copy of the Adobe Acrobat Distiller Directory.
Remark: The following method has been testet with Adobe Acrobat 3.01 and 4.0 on Macintosh 8.6 and 9.2. If this does not work with an other Acrobat Distiller version and an other computer operating system there are other methods instead of using the Distiller Startup directory. The following is only an example. Organize the Hard disk as follows:
Distiller directory subdirectory Startup includes one default file: Example.ps
Copy of the Distiller directory subdirectory Startup includes the default file and one user file: Example.ps and S84E00FP.DAT
The copy of the Distiller directory differs only by the file S84E00FP.DAT in the Distiller Startup subdirectory. For a screen foto with this kind of organisation see
DISTILLER.tiff (70 kByte)
Fig. 7: Screen foto of the organisation of the original and the copy of the Distiller directory with a user file in the subdirectory startup.
The following steps are necessary for the application
Step 1: Produce a copy of the directory Adobe Acrobat Distiller 3.0 or later
Step 2: Copy the file S84E00FP.DAT into the subdirectory Startup of Adobe Acrobat Distiller 3.0 or later which includes the default file Example.ps.
Step 3: Produce from the NP file L84E00NP.PS two copies X84E00NP.PS and Y84E00NP.PS. Delete in the second the lines between %BEG DE84 and %END DE84 (line 21 to 57). There is then no PS MTL code in the second file. Change in the two files the text "L84" to "X84"and "Y84" for output identification, if an appropriate editor with "search" and "replace" is available (this step is optional).
Step 4: Use the PS file X84E00NP.PS and produce the PDF file X84E00NP.PDF with the original Adobe Acrobat Distiller (in the subdirectory startup there is only the default file Example.ps, see above).
Step 5: Use the PS file Y84E00NP.PS and produce the PDF file Y84E00NP.PDF with the copy of Adobe Acrobat Distiller (in the subdirectory startup there is the default file Example.ps and the user file S84E00FP.DAT).
Step 6: Compare on the monitor the output of the two files X84E00NP.PDF and Y84E00NP.PDF in two windows of Adobe Reader 3.0 to 5.0.
If the software Adobe Reader 3.0 to 5.0 is used (e. g. on Macintosh OS X 10.2) then there is a disagreement with basic user requirements and colorimetry. The PDF file X84E00NP.PDF includes two different corresponding PS input operators and produces two different colour scales (not expected). The PDF file Y84E00NP.PDF produces two identical scales and all scales are darker compared to the first one (as expected by the PS MTL code).
XY84R0NP.tiff (250 kByte)
Fig. 8: Screen foto of the two files X84E00NP.PDF and Y84E00NP.PDF for the CMY output which are both viewed by the software Adobe Reader 5.0 (on Macintosh OS X 10.2). For similar files with the OLV output see XY85ERNP.tiff
if the software Mac OS X Preview is used (e. g. on Macintosh OS X 10.2) then there is in agreement with basic user requirements and colorimetry. The PDF file X84E00NP.PDF includes two different PS input operators and produces two identical colour scales (as expected). The PDF file Y84E00NP.PDF produces two identical scales and all scales are darker compared to the first one (as expected by the PS MTL code)
XY84P0NP.tiff (250 kByte)
Fig. 9: Screen foto of the two files X84E00NP.PDF and Y84E00NP.PDF for the CMY output which are both viewed by the software Mac OS X Preview (on Macintosh OS X 10.2). For similar files with the OLV output see XY85P0NP.tiff
Summary: Both the software Mac OS X Preview and the PS MTL code is in agreement with basic user requirements and colorimetry. The software Adobe Reader 3.0 to 5.0 is in this point not in agreement with the basic user requirements and colorimetry. Fig. 9 shows the difference. In the left figure the PDF file X84E00NP.PDF includes two different PS input operators and two different colour scales are produced (not intended) by the software Adobe Reader 3.0 to 5.0. In the right figure for the same file two identical colour scales are produced (intended) by the software Mac OS X Preview.
X84RP0NP.tiff (250 kByte)
Fig. 10: In the left and right figure the same file X84E00NP.PDF is viewed by the software: Adobe Reader 5.0 and Mac OS X Preview. The corresponding colour scales (left and right in each figure) are not identical for the software Adobe Reader 5.0 and are identical for the software Mac OS X Preview as expected by colorimetry. For similar files with the OLV output see X85RP0NP.tiff
Interpretation of the different figures: If the PDF file Y84E00NP.PDF is produced from the PS file Y84E00NP.PS then the copy of Adobe Acrobat Distiller takes the PS MTL code which is in the corresponding Distiller Startup directory. The change from two PS input operators to one PS output operator and a square root output (darker grey scales) is produced by the PS MTL code of the file S84E00FP.DAT (identical to S81E00FP.DAT) which is included in the subdirectory Startup of Adobe Acrobat Distiller 3.0 or later.
The PS input operators:
1. cmy0* setcmykcolor and 000n*
setcmykcolor
2. olv* setrgbcolor and w* setgray
are transferred by the PS MTL code (which is in the startup directory) to the PS output operator no. 1
1. cmy0* setcmykcolor and 000n* setcmykcolor
For the FP file the output of the four 16 step colour series is the same on the monitor with Acrobat Reader and the output is equally spaced (if the start output LAB* data are determined and included in the file S84E00FP.DAT).
Conclusion: The second PS file Y84E00NP.PS does not include any PS MTL code and therefore any PS file may be used with any mixture of the above two PS input operators no. 1 and 2 for the intended corrections.
5.0 Comparison of the above example solution with the two basic user requirements
The first basic user requirement
is that the same colour scales are produced and the
second basic user requirement is that a linear relationship
is produced.
There is a linear relationship between the input w* data (or the n*=1w* data) and the output lightness L* data of the 16 step grey scales. Therefore a mean grey L*m = 0.5 (L*w L*n) is produced for w*=n*=0.5.
By the PS MTL code the corresponding feature is reached for the colour scales between white and the 6 colours cmyolv*. The situation is similar for the six colour scales. For linearization it is required to include the CIELAB start output data are in the FP file or the Distiller Startup directory.
The above example solution fulfils both basic user requirements.
Final result: The Colour Workflow (CW) and the Output Linearisation (OL) of the PS MTL code is based on ISO/IEC 15775 and DIS ISO/IEC 19839-X. The PS MTL code is compatible to CIELAB and fulfils the basic user requirements in the field of image technology.
This result for colour scales is identical to the final result in DE811 for the achromatic colours.
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