Note: this is the third part of a multi-part post. Click here for the first post in this series.
Targen generates a numerical representation of the target, independent of the output device and of the measurement device used. Printtarg is the program that converts the .ti1 target in a series of .tif images ready to print, and an accompanying index file that describe the color value of each patch in the target charts according to their position in the charts. Printtarg optimizes the placement of the individual color patches in the charts to ensure a successful read by the targeted instrument. This is particularly important for ‘swipe’ type colorimeters, which can read a whole chart line at a time. These instruments rely on a significant difference in color between one patch and the next to know the boundary between patches. Printtarg will report in its diagnostic output the minimum ‘DeltaE’, or color difference, between adjacent patches in the target charts. Here a big number is desirable, the exact opposite of the normal use of DeltaE as an indicator of the residual error in a color managed workflow.
Here is our standard syntax for printtarg:
printtarg -v -iCM -h -T360 -p11x17 printer_paper_target_name
For all of the available options to printtarg, see the online man page here.
|-v||Verbose mode. Prints diagnostic information to the console as printtarg progresses|
|-iCM||Defines the instrument that will be used to read the chart. CM selects the ColorMunki, many other options are available|
|-h||Selects high density mode for the ColorMunki. This will generate smaller patches so that more can fit on a printer sheet, but will require a little more care during reading|
|-T360||Instructs printtarg to generate 16-bit tiff images for the charts that comprise the target. The 360 defines the resolution of the chart images in PPI (360 PPI is the resolution we use on our printers). If an 8-bit chart is desired, use –t360 (lower case t).|
|-p11x17||Sets the paper size for the charts to be generated. In our case, we use 11×17 as it fits on either 17” roll paper or B/B+ sheets. Many other options are available, and custom sizes can be specified as HHHxWWW in millimeters.|
|printer_paper_target_name||This is the base name for the target being generated. Note that no extension is specified. Printtarg will open the .ti1 file generated by targen and will create a .ti2 file along with printer_paper_target_name_01 through _nn.tif image files|
The .ti2 file includes the data from the .ti1 file with additional information identifying the format of the target (number of patches per row, number of rows, number of charts) as well as the individual expected color data for each patch tagged with the patch coordinates within the target.
Here is an example of a chart (1 of 5) generated with the above printtarg syntax:
You are now ready to print your calibration targets! Make sure that you set your printer driver options in the same way you will be using to print your fine art images with the profile you will generate. Make absolutely sure that neither the printer driver or the application you are using to print are implementing any sort of color management. This is sometime confusing, and downright not possible in Photoshop CS5. To ensure the desired results, the best way we found is to use a purpose built, free utility from Adobe, called Adobe Color Printer Utility. Open each of the .tif files in ACPU, print it to the target printer (again, make sure the driver is set for no color management), sit back and watch your target charts appear! I recommend you print all the charts and let the ink dry and cure for at least 20 minutes before you start the reading process. Inkjet ink is known to drift in color during the first 10 to 20 minutes of drying. If you are profiling specialty substrates, especially high gloss plastic film types, you might want to allow additional drying time to ensure that the colors have stabilized before you measure them. If you are profiling a substrate that requires coating with a liquid laminate (I.e.: fine art canvas) make sure that you apply the laminate to the target charts and let it completely cure before you measure the charts.
After your target charts have had a chance to dry, you are ready to read them with your spectro! Click here for Part 4, where we address chart reading with the ColorMunki..