Note: this is the second part of a multi-part post. Click here for the first post in this series.
Profiling a new paper/printer combination always involves the key step of printing a series of charts consisting of multiple color swatches, and measuring them with either a ‘spot’ or ‘swipe’ instrument. In most commercial profiling software packages the targets are usually predefined, and only a limited selection is available.
In general, the larger the number of patches the better the final results. Also, in general, the larger the set of target supported the more expensive the program.
Argyll CMS has no predefined targets. Instead, it provides a program that can generate any target the user desires, targeted for a wide variety of RGB, CYMK and multi-colorant printing processes and with any user defined number of patches.
This program is, intuitively enough, called ‘targen’, and it is the first step in the process. We suggest starting the process within a new folder named for the paper being profiled, to make it easier to keep track of all the files that will be generated. In the examples to follow we will be using a Mac computer running OS 10.6, but the command line syntax is identical across Mac OS, Linux and Windows.
Here is the syntax of the targen command as we use it in our workflow (note, options are case sensitive, and should be used exactly as shown):
targen -v2 -d2 -G -g128 -e8 -f2264 paper_printer_target_name
And here is an explanation of the options we use (a summary of all options can be quickly reviewed by issuing the targen command with no option, or by reviewing the online documentation).
|-v2||-v controls the verbosity the program output during execution. Level 2 provides us with our desired level of diagnostic output|
|-d2||-d chooses the colorant combination for the targeted output device. The value 2 indicates an RGB printer (the proper choice for most inkjet printers, even if they really use CYMK based inks)|
|-G||-G instructs targen to generate good optimized target points as opposed to use a fast algorithm. We are after quality, and we don’t mind a little more processing time.|
|-g128||-g (watch for the case) controls the number of pure neutral patches that will be included in the target. A clean rendition of neutral tones is a key feature of a good profile, so we include 128 neutral patches. Targen will generate 128 equally spaced patches between pure black and pure white.|
|-e8||-e controls the number of pure white test patches included in the target. We chose to have 8 white patches.|
|-f2264||-f controls the total number of patches that will comprise the calibration target. A feature of high grade profiles is that usually are generated from 1728 (12^3) or more samples. This minimum number provides at least 12 levels for each RGB primary and all possible combinations of those primary. In addition, we like to have at least 128 neutral levels and 8 white patches, for a total of 1864. We picked 2264 as that is the number of patches that will completely fill 5 11×17 sheets (the above patch set overflows 4 sheets) when printed for a ColorMunki in high-density mode. Feel free to chose a different number to optimize the paper size and instrument combination you are using. Up to 3,000 patches can be used for best quality inkjet output profiles, before reaching a point of diminishing returns.|
|paper_printer_target_name||This is the base name for the target (and the eventual profile) to be created. For simplicity I do not recommend the inclusion of spaces in the file name, but if you want to do so make sure to include the file name in double quotes as “paper printer target name” or expect syntax errors!|
Targen will set off to work, printing diagnostic messages on the console as it progresses. You will likely see some warnings as targen attempts to generate equidistant color samples and in some cases cannot perfectly space the individual samples, especially when you ask for 2,000 patches or more. Take these as information but they are not critical and can be safely ignored. Once targen concludes, you will find the file paper_printer_target_name.ti1 in the working directory. This is a text file that can be viewed with any text editor (no need to do so, except for personal edification). This is another great feature of Argyll CMS: all the internal data is easily readable and if necessary editable – not so with most proprietary packages!
Congratulations, the first step is done, and you survived the command line! Click here for the next step!