The Custom Black script is designed to generate a Black, Light Black and Gray channel as needed. I had found that in my work I occasionally required just a Black or a Gray channel, and that instead of running the full color separation script it would be nice to have a script tailored just for this. And so was born the Custom Black, as well as it’s partner the Custom White.
Part of the overhaul of the YRGBK script was a refresh of the Black module. While the core approach remains the same, I spent a lot of time looking at how the interface is used, as well as how to improve the techniques and quality of the channels. The result was a much improved Black generator with better options and usability. The Custom Black script uses the same Black module as the new YRGBK script, with a few additions for generating the channels mid-separation.
The Main Window
The first window in the script provides sliders for controlling how much color masking is applied overall to both the Black and the Gray. Most adjustments for a particular type of color separation or set up can be done with these sliders. Bright images with primary colors and key lines can use a black that is turned way down, while photographic images will work best with the default settings. The slider range is now 0% to 100%, with higher values printing more Black into the colors.
In addition to these sliders, you can open open more advanced dialogs as well as generate a Gray, the Gray Component and a Mask channel from the main window.
The Black generator and the new Saturation Mask Options
In the secondary window for the Black generator I added more options to control how the Mask is generated and applied. This finer tuned control improves both the results of the script as well as its flexibility. With the addition of Tint, Tone and Shadow sliders, the amount of black printing into the colors can be adjusted for different value ranges, while the color sliders allow adjustments for particular colors.
The Saturation Mask revisited
The main component of the Black generator is the mask that limits the amount of black printing into the colors. This is called the Saturation Mask, as it is derived from the color saturation of the image. Starting with the images Luminosity, the mask is applied along with a gain adjustment and color balancing to create a printable black. In the New Black generator I have included more options for adjusting the variables that go into this mask, as well as how the mask itself is applied.
Gray Component remade
In addition to Black, the script can generate a light black I have called the Gray Component.
In a CMYK separation, the lighter grays and the neutral mid values are handled by the Cyan, Magenta and Yellow channels. This makes for good tonal qualities, but makes a CMYK Black challenging to use for a spot color separation as it tends to be missing these values. The technique used for this is called Gray Component Replacement, or GCR.
The concept behind the Gray component channel is to generate a channel that prints all these gray values, as well as the values that darken the colors in an image, and to remove these values from the Black channel. This opens the possibility to print the Gray Component as a second Black using a transparent ink, while using a dense Black ink for the key lines. A Custom Black generated with a Gray Component channel will resemble a CMYK black.
While the Custom Black script has always had the Gray Component option, the current version is much more advanced and is optimized for printing. The Black, Gray and Gray Component channels all work together to provide more options for managing the values in a color separation.
Gray Ramp for Gray and Gray Component
In addition to the Saturation Mask, the script also uses a curve adjustment to generate the Gray and Gray component, called the Gray Ramp. The Gray Ramp determines which values go to the Gray channels and which go to the Black. With the current build for the Gray channels I moved the Gray ramp to a new window just for generating the Gray and Gray Component.
I have also added a function called equalize which balances the black printing over each color. This can be turned off if you prefer to make custom adjustment after the black is generated.
Imagine, implement and calibrate
It is hard to overstate the amount of effort I put into the new custom Black module, but I can say with confidence it was worth it. The new Black module is perhaps the most refined component I have created, and I appreciate this every time I use it. A Black screen can make or break a print when it gets on the press, so making sure the Black is perfect may just be the most important part of the color separation process.
For detailed description check out the manual for Custom Black in the tutorials section: