You will now get to the part to define the black generation of your printer calibration. This process allows determining which combination of inks provides the best black as well as preventing dithering from black ink in light areas if you don't have a gray ink in combination.
hueman v2 Black generation provides 3 methods to generate the black ink:
Default (Black Only)
This method is recommended if you have very good, strong black ink in your printer and if you also have gray ink (light black) that prevents dithering from the black ink in light areas. In this case, the black generation will be black only.
This method is recommended if a combination of inks is better than your pure black ink only and if you also have gray ink (=light black) in the printer to prevent dithering from the black in light areas. Here, the black generation will add the defined values of the additional inks to improve the overall darkness of the result. You can use the "Print.." button to determine whether a combination of colors including black is better than the black ink only.
Gray Component Replacement (GCR)
This method is recommended if a combination of ink is better than your pure black ink and if you don't have gray ink (=light black) in your printer. With this method CW8 will replace light areas of black with a combination of CMY inks, to visually minimize the dithering from the black ink. Be aware that such a GCR can be critical since the light fastness of C, M, and Y are not always the same and that after a certain time, one of the inks might fade faster than others resulting in a non-neutral behavior of gray areas (e.g. outdoor flag printing).
GCR Presets for DTG
We had one only standard GCR curve, but for DTG we felt is not enough: in some cases, we would use a larger amount of white ink, and in some cases less. The feeling when touching a t-shirt with different amounts of white is quite different. That's why we created two new presets for black and gray media modes:
- DTG-HQ will use a thicker white base and will have better colors and the worst touch.
- DTG-Eco will use a thinner white base and have better touch and lower consumption, but colors will be duller than in DTG-HQ.
Patch Chart File
In order to evaluate whether a combination of ink is better than your pure black ink, you can use the "Print.." button to print out a chart for visual analysis. You can select one of the charts in the list.
Note that the multichannel file is a special color mode in Photoshop and may not contain CMYK or RGB color channels on top. Save them in .psd format.
For most printers, the BlackAdd_CMYK.psd (or the smaller A4-sheet-fitting BlackAdd_cmyk_A4.psd) will be enough.
If you have additional process colors, such as Orange, Blue or Red (not light inks!), you can select the according to the patch file.
Example: If you have loaded Cyan, Magenta, Yellow, Black, Gray, Orange, Blue, and Red in your printer, chose the BlackAdd_CMYK+3.psd (or _small.psd). Since Gray is a light ink, do not count it as +1 ink.
With the button "Add…" you can add individual charts to print if you would like to test another set of combinations. Be aware that the chart MUST be in a multichannel format so you can arrange the channel order in the "Print.." window. We recommend that you put at least 4 spot channels and name them Cyan, Magenta, Yellow, and Black so that CW8 can auto-assign them to the proper ink channel.
Print the selected chart for visual analysis. In digital textile printing, you should steam and wash the chart since you want to see the final result (as with all charts except with the ink limit charts in most scenarios).
The default charts contain different combinations of black with the other process colors. In the center of each patch, you'll find 100% pure black ink. Around the center is 100% black plus the combination of inks with the values noted aside. If you really find a black that is better outside than inside (better=darker and/or more neutral, etc.) you can use these values to fill them into the "Rich black" fields.
In the example above, the red-circled patch has a better black outside than in the center. We will use K100, C60, M60, and Y60 for the "Rich black" fields for either Black Addition or GCR.
Do not use extreme combinations, such as K100, C90, M90, Y0, since you might encounter other problems that are not seen in this chart (e.g. light fastness, steaming stability, etc.). We recommend to use a combination containing all values, such as K100, C60, M60, Y30 or K100, C30, M30, Y30, for stability purposes.
Of course, only select a "Rich black" if the combination is really better than the black only since you will increase the ink amount, leading to higher production costs. Fill the determined values into the fields. You can only use "Rich black" in combination with Black Addition or Gray Component Replacement method.
The advanced settings of black generation are provided format experienced users only. Usually, using the regular black generation window will be sufficient to get a high-quality profile.
Advanced settings allow you to fine-tweak or control certain printing environments, but it can also lead to wrong results if not used properly. Proceed with care and use the default settings, whenever possible.
- Revision: By default, CW8 will automatically select the latest color separation technology in the revision list. The latest revision usually delivers the best result for each specific ink combination. We recommend not to change the revision unless specifically instructed by your distributor or by Inèdit.
- Profiling mode: The default profiling mode for neoStampa is RGB profiling. The profiler included in CW8 (optional license) that creates the ICC profile will only work if RGB is selected. In addition to this, all configuration parameters in the black generation will only be available with RGB profiling mode. CMYK profiles can also be generated. However, CMYK profiles are basic because no parameters of any kind can be selected for their generation- you will notice that most of the options in this window become inactive when this mode is selected. The black generation using CMYK profiling is usually defined by an external profiler.
- Balance: The "Balance" parameter allows for to increase or decrease of individual inks to balance the black generation combination using Black Addition or GCR. Since the profiling process will correct irregularities in the balance between inks, the "Balance" option is not really required, and the values should be left at 1.0 In very rare occasions, a certain ink may be much stronger (or weaker), in relation to others, and can be corrected here. The resulting curve will be displayed in the Black generation preview, on the right of the window.
- Black start: The curve control area allows the specification of certain conditions on the curve, such as Black start, Body (light), and Body (dark). The Black start sets the start position of the black ink to the defined value.
The default value for Black Start using Black Addition is 33%. It means that the additional colors to achieve a richer black will start to enter after 33%, and will reach the specified value at 100%. Below 33% only black ink (including gray) will be used.
- The default value for Black Start using GCR is 20%. This means that below 20% of the black generation, no black ink will be present, but instead, it will be replaced with a combination of C, M, and Y inks. This is to prevent dithering of the black ink if no gray ink (=light black ink) is present in the ink set.
- Body (light): The Body light parameter shapes the curve in the lower area of the black generation. The ideal value is experimental but should result in a smooth and regular total curve shape, which can be seen in the Black generation preview. The default value for Body light using Black Addition is 83. The default value for Body light using GCR is 33.
- Body (dark): The Body dark parameter shapes the curve in the upper area of the black generation. Also here, the ideal value is experimental and should result in a totally smooth behavior of the final curve as seen in the Black generation preview. The default value for Body Dark using Black Addition is 100. The default value for Body (dark) using GCR is 66.
- Ink limit method. neoStampa includes two methods for ink limiting:
- Smooth: The default method provides intelligent ink limiting without clipping behavior in heavy ink load areas. It optimizes the ink amount in extreme areas to provide smoother behavior of gradients but sacrifices 2-3% of the gamut.
- Clip: The clip method just cuts down the exceeding ink to the defined value. Although the gamut might be 2-3% larger in these extreme areas, it is possible that gradients in very dark areas are not as smooth as with the above method.
- BlackOptimizer ®: This function improves the gamut behavior in colorful areas when moving towards saturated, dark colors. Since especially in digital textile printing, the regular GCR method doesn't always directly make a color darker but turns it duller and sometimes even lighter, intelligent analysis of color-to-dark is required, to improve the combination of colors in the black generation. BlackOptimizer does this analysis based on whether a color is already dark and therefore uses less GCR to get darker. It is recommended to leave this button always on. If you encounter some dithering from color to dark (e.g. if the black ink starts too early), it might help to switch the function off, although it might make the printer gamut less linear.
- Shadow dot gain: A dot gain can be added to improve overprinting of colors, also in darker areas. An insufficient saturation in dark areas is sometimes caused by an intermediate ink limit behavior, which causes a bump between the absolute ink limit (2-mix-colors) and the relative ink limit set in the RIP (e.g. 240%). A regular dot gain is usually applied to all colors, but from the CIELab point of view, the linearity is not given anymore. The Shadow dot gain parameter adds a dot gain only where is it required; in already saturated colors, to counteract the bump effect. The default value of 15% is a good balance between improving the bump effect and laying down too much ink but mainly depends on how heavily the colors have been linearized.
The Early black improves the gradient and linearity from dark-saturated to dark-unsaturated color, affecting the black ink directly in normal cases, and should be switched on by default. Switch it off only if you experience strong jumps in dark-unsaturated areas from the black ink or a rich black combination.
How to make new printer calibration