Setting the Black and White points

Setting the Black point seems to come up quite a bit , so I thought I should post about Black and White points.

RGB Black Point
The Black point is the Darkest set of pixels in an image, while the White point is the Brightest. By setting the darkest and lightest pixels to 100% Black and White, respectively, we can increase the tonal range as well as the contrast in an RGB image. This step also ensures that any solid areas of Black or White are set to print with 100% coverage. Increasing the tonal range and contrast in the RGB mode will always improve the results from the YRGBK script.

The Levels dialog. To change the black point move the Black arrow.
To change the black point move the Black arrow.

Levels or Curves
There are several ways to approach setting the Black points, but for the most part in Adobe Photoshop we can use either Levels or Curves. Both tools can do the trick, but for the most control over the results I always go for the Curves. In Photoshop’s menu go to:

Image/Adjustments/Levels
or:
Image/Adjustments/Curves

The Histogram
A histogram is a graphic representation of the pixels in an image. The Levels dialog is a Histogram with sliders, where the left side represents the dark values and the right side is the light values. The number of pixels in a value range is represented by a line going up from the bottom, so the taller the line in the graph the more pixels in that range. The Arrow on the left sets the Black point, while the arrow on the right sets the White point. The Curves dialog can also display a Histogram if you check the Histogram checkbox.

Convert to Adobe RGB to expand the color gamut.
Convert to Adobe RGB to expand the color gamut.

The Techniques
In this tutorial I am actually going to describe two techniques for setting the Black and White points in Adobe Photoshop’s RGB mode. Which approach you use depends on the image and your goals. The best place to start is by converting an image to Adobe RGB, if it is not already.

•  Edit / Convert to Profile..
Destination Profile : AdobeRGB (1998)

 The Droppers
In both the Levels and curves dialogs, there are three eyedropper icons on the right or along the bottom; the left one sets the black point,  the right one sets the white point, while the middle dropper sets the neutrals.

The droppers set the Black and White points.
The droppers set the Black and White points.

Open the Levels or Curves dialogs:
• Double click on the Black eyedropper to open its color dialog. Set the color to 100% Black. Do the same for the White, setting the value to 100%.

Now, when you select an eye dropper and click on the image, that value will be set to 100% White or Black.

• Select the Black eyedropper, click on the darkest area in the image to set it to Black. Do the same with the White eyedropper, setting the lightest areas to white.

The Middle dropper can be used to set the neutral values in an image. This can be helpful with photographs taken with the wrong lighting settings, or if you have a gray card in the image. This dropper can cause a large color shift in the image, and is not needed to set the Black and White.

The Dropper approach is good for photographs, especially if they lack contrast or had poor lighting. It can also be a quick way to set a Black or White point on simple separation.

Using Curves
The Droppers may cause a noticeable shift in color, and in some cases we just want the light and dark areas adjusted. We can manually set the points using the Curves dialog, while keeping the middle values in place, to avoid color shifts.

Setting the Black and White using Curves.
Setting the Black and White using Curves.

Single Step
Open the Curves dialog:
In the curves dialog we can also set the Black point by moving the 100% point on the curve to the darkest pixels in the image.

• Start by setting the Show Amount to Pigment/Ink %
• Check the Histogram check box.
• Click and drag the 100% point to the first set of pixels in the histogram. Do the same for the 0% point to set the white.

If you click and hold on the image with the curves dialog open, you will get a reading in the dialog showing the original and new values. This can be used to measure the values in the image. If you Cmnd click in the image, or click along the curve line, you can set a point on the curve.

To avoid making color shifts we can break this adjustment into two steps and set values along the curve.

Two Steps
Open the curves dialog:
• Set points along the curve by clicking in the image or along the curve line. Set points below 50%.
• Slide the 100% point to the darkest pixels in the histogram. This value can be determined by measuring in the image.
• Adjust the curve if needed for a good tone transition.

Setting the Black point manually using curves.

Click OK and repeat the process for the White. This time setting points above 50% and moving the 0% point to the right.

This is a good approach when we need to set the Black and white, but do not want to shift the colors in an image. It also gives good control over the resulting value transition. In this example it shows in the white where it fades into an off white shade, and I could soften my curve to smooth that transition out.

Setting the white point manually using Curves.

 

Setting the Black and White points of a color channel in a separation
We can also look at the Black point of each channel in a color separation to be sure they have good contrast and range. The techniques are the same as above, with a single color channel selected.

Color channels generated by the YRGBK script have their black points set based on the saturation and brightness of the ink colors. We can customize these colors by changing the black point of a channel, and adjusting the channels ink color to match.

It is also helpful to adjust the Black point when a channels darkest values hover over 90%. We can shift the value to 100%, while setting points on the curve, and improve both the coverage and range of the color.

Applying a 2% clean up curve to all channels is a good idea.

Finally, the white point of a color channel should be inspected to avoid random dots and 1% areas, which can be a problem when making screens.

Setting the Black and White points is a crucial step that is often overlooked. Ensuring  good value ranges and solids in an image from the start will always improve the results.

The Color Separation Workflow

Preparing a color separation for screen printing can be an involved process. We can break the process into several distinct stages, however, to make a manageable workflow. I cover each step in some detail here on this site, but for this post I want to tie them all together. While each stage can have it’s own series of steps, here I will outline the main parts, while including links to detailed explanations.

Preparing the image –  File preparation
This first step is easy to overlook, but careful attention at this stage can make the entire process easier while improving the results dramatically.
There are three main parts to this step:
1. Setting the images Black and White points
2. Cleaning up the image
3. Removing the background

Creating a Base SeparationThe YRGBK Script
Although many color separators will jump right in and start building a color separation from the prepared image, I have found it is helpful to start with a base separation generated using a standard process. There are several advantages I find with this approach.

First, a decent color separation algorithm can get you a good ways down the road towards a finished product, while a great one can get you pretty close to the finish line, depending on your needs. Elements like a Base white, HIghlight White and Black channels can be created consistently from project to project, while color channels can be generated in a way that ensures all color information is present.

Finally, it can be helpful to leverage the knowledge of an experienced color separator when using an scripted algorithm or technique for this process. The YRGBK Script was developed for this purpose.

Customizing the Separation.
The best results are obtained when a color separation is designed to accommodate not only the image, but also the printing technique and substrate it is being printed on. Whether it is splitting solid colors from halftones for textile printing, or converting primary colors to Custom colors for color matching and ink coverage, the results are always worth the effort.

Clean up and review.
Once the separation is complete it is good to have a review process and clean up stage. I like to make this a defined part of the process so I do not get bogged down in clean up while I am trying to customize a separation. It is also helpful to ensure the image has been cleaned up and to take a final look at how the colors are going to print. Stray 1% dots, 98% solids that should be 100%, and misplaced custom colors can all be handled easily at this point, while providing potential headaches if they make it on to the press.

Convert the gray values to printable dotsSimRip 3
Since a color separation is generated using gray values in our channels, it is necessary to convert these values to printable dots which can be imaged on the screen or plate. Dot Size,  Shape and Angle all play a part in not only the look and feel of the print but also in the quality of the result.

Whether I am printing to the Direct to Screen printer at the shop, or making film in my art studio, I have found significant benefits to handling this conversion within Adobe Photoshop. Even though I may be printing to an actual Rip, which traditionally handles this step, the flexibility and control as well as the ability to carefully review the output has led me to converting every job to halftones within Adobe Photoshop.

Output the Color separation to film, plates or screens.
Finally, with the separation complete and converted to halftones, the channels are sent to the printer.

Saturation and Color Density in YRGBK 2.3

(Another post in a series on using the settings in the YRGBK script)

The color Density, Color Saturation and Auto settings
The color Density, Color Saturation and Auto settings

The Saturation and Color Density sliders in the YRGBK script can be used to adjust the amount of color in your final separation. Although both adjustments appear to have a similar effect, the results of each are very different and they can be used together.

Setting the Black point for each channel In the Custom Color dialog.
Setting the Black point for each channel In the Custom Color dialog.

Color Density
The color density slider adjusts the Black point, or how dark the darkest pixels will be, for all color channels. Each color channels black point can be set individually using the Custom Colors dialog, while the Color Density slider adjusts all the channels together.

The Black point of the color channel determines the amount of ink being printed overall, and is balanced with the color of the ink itself. If we are using a duller, less saturated ink we can increase the density of the channels to compensate. If our inks are pure primary colors we can decrease the density levels. With the Color Density setting set to 0, the black point for all channels is set entirely by the custom color sliders.

Auto
 The Auto check box automatically sets the darkest pixels to black in each color channel. This setting overrides the values applied in the Custom Colors dialog, so the results can be unbalanced if the image does not contain a full set of primary colors. The Auto setting is useful, however, if you intend on customizing your colors. The Color Density slider increases the Auto amount for all color channels.

Saturation
The Saturation slider applies to the mid range values in a channel. The Darkest pixels in a channel are not made any darker, but the amount of ink overall is adjusted. The default setting is 50, which means that pixels in the 50% range will be set to 50%, or no adjustment.

Increasing the Color density affects the dynamic range.
Increasing the Color density

Dynamic Range and Coverage.
Dynamic range is the difference between the lightest and darkest values on a channel or in an image. A print with good dynamic range will have high contrast and be able to reproduce the full range of values in an image.
Coverage is how well an ink deposit covers the substrate. For screen printing on textiles it is nice to have an ink printing at 100% coverage where the color is brightest. Most printers will try to achieve a solid print in areas covered by a single color. If the channel itself is coming in below 100%, the print pressure will be increased to create a good ink surface. The resulting dot gain from increasing the print pressure will reduce the dynamic range.
We can anticipate this by setting the solid areas on a color channel to 100%, allowing for complete coverage while maintaining the range of values the color can reproduce. This is only possible where a color in the image is a pure primary, or we are using a custom ink color.

Increasing the Color Density while decreasing the Saturation
Increasing the Color Density while decreasing the Saturation

How is this used?
If our inks are duller or our image brightly colored, it can help to increase the density of the colors. Pushing the darkest values closer to 100% increases the dynamic range of each channel, increasing the range of colors that can be achieved.
If the separation itself is too dull or too colorful overall it can be helpful to adjust the Saturation slider. Since this adjustment does not affect the black point the dynamic range and maximum density of the colors are not changed.
Finally, if we are planning on using custom colors, the Auto setting can be used with the density slider to quickly set the black point for all channels so the densest areas of color are printing at 100%. In this case the Saturation slider value can actually be reduced in order to maintain the mid range.

The result of increasing the color density
The result of increasing the color density compared to the default settings
The result of Increasing the Color Density while decreasing the Saturation
The result of Increasing the Color Density while decreasing the Saturation, compared to just increasing the density.

The Custom Black, Custom White and Gray sliders

Another post in the series on the new YRGBK 2.3 script.

In the YRGBK 2.3 script, the Black, White and Gray sliders control the amount of each ink printing into the colors. The effect is to brighten the image by letting the colors show through. The level of brightness is controlled by the sliders; higher values in the slider increase the amount of ink, while lower numbers decrease the ink levels. Controlling the amount of Black in an image’s colors is useful for images that are either brightly colored or contain a lot of detail.

The Saturation Mask
The adjustment applies mainly to areas of color. The Script generates a mask using the saturation values in the image. The greater the intensity of the colors, the heavier the Saturation Mask will be. Detailed adjustments can be made in the Custom Black dialog, using the Saturation Mask settings, by checking the Custom Black Checkbox.

Uses
if I need more detail in my colors, or if my colors are highly saturated, I can increase the value in the slider. if I need less, say for instance I have an image with pure solid colors and a black line, I can decrease the black slider to clear the black out of the colors. The default settings are balanced with the colors assigned to the color channels.

The Gray Slider in YRGBK 2.3
The Gray Slider
The White Slider in YRGBK 2.3
The White Slider
The Black Slider in YRGBK 2.3
The Black Slider

 

Use Ink Colors in YRGBK 2.3

This is the first post in a series I will be doing where I will be talking about various functions in the YRGBK script, what they are doing in the process, and how you can use them.

Terms:
Hue is the color of a channel

Saturation is the amount of a color
Value is the brightness of a color
Gamut is the range of printable colors the color model can achieve

Use Ink Colors
The YRGBK script splits the colors in an image based on the Hues and the Values, with all of the Value information going to the Black, White and Gray channels. The Hues are then split into a set of primary colors, and, if the Use Ink Colors box is checked, assigned printable ink colors. The Black channel is adjusted by default to work with the printable colors.

Color Gamut
When a color in an image falls outside of the ink color set used for printing the color is said to be “Out of Gamut”. This can cause color shifts in the image when running a color separation through the script. By Unchecking the Use Ink Colors check box, we can keep the colors in their original, primary state. This creates a separation with a much larger color range.

If, when running a separation through the script you notice a large color shift, it can be helpful to turn Use Ink Colors Off to visualize the whole color gamut.

To generate a Primary color separation:
• Uncheck the Use Ink Colors checkbox in the main window
• Check the Custom Black box
• Check the Custom Colors box

Adjust the Black Values
In addition to setting the color values, the YRGBK script makes adjustments to the Black channel to accommodate the brightness of the ink colors. When Unchecking the Use Ink Colors option, there will not be enough Black generated to render the image fully using the default settings. To fix this:

• Set the custom Black slider in the main window to 100.
• In the secondary Black Generator window, set both the Midtone and Shadow values to 0.

Adjust the Saturation Levels
 Color channels are also adjusted for Saturation levels by the script. The Colors in the primary set have a saturation of 100%. Ink colors, on the other hand, have much lower saturation values based on the selected inks.

For most images the default settings are calibrated to generate good results using the Ink colors. For some images we need to adjust the density of the channels to achieve proper saturation levels. The Color levels sliders in the Color Generator dialog adjusts each channels density individually. To reset the color adjustments for a primary color separation:

• In the Main window, set the Color Density to 0
• In the secondary Color Generator window, set all the color sliders to 0, the Midtone to 100, and uncheck the Transition Mask box.

Conclusion
The Use Ink Colors option is checked by default, and in most cases this is where you will want to leave it. This setting will automatically bring your colors into a printable range that works with the default settings in the rest of the script. Often it is easier to customize the color channels after running the script then it is to run a primary color separation and make it printable. A primary color separation generated in this way would need to be manually adjusted to achieve printable results.

That said, in the case where you have large color shifts, unchecking the Use Ink Color dialog can quickly create a wide gamut, fully saturated color separation. Creating a primary color separation in this way can help to visualize a solution, or can be used as a starting point for working the separation up manually.

The new Custom Black

The Original
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.

The New
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.

Balancing act
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:

Introducing SimRip 3

Introducing the latest version of the pioneering Halftone converter for Adobe Photoshop® SimRip 3

Ready to print Custom Halftones within Adobe Photoshop.
SimRip3 has been re-imagined with all an all new settings window displaying the Channel Names as well as the Dot Size, Angle and Shape.

The SimRip 3 dialog with channel names and more options.
The SimRip 3 dialog with channel names and more options.

Custom Halftones
With the custom Dot pattern controls in the main window, SimRip 3 provides a quick way to generate several of the most popular halftones.

New shape options have been added and now include a Halftone Line and a Round Dot, with the Standard Ellipse. Getting your separations into printable, custom  halftones, has never been easier.

Print Preview
The new preview option can be used to generate a document which includes the printers dot gain. This is extremely helpful for visualizing results and making adjustments.

Print Preview documents can be printed to an inkjet printer as a full color image, providing hands on previews of printed material. See the video above to see Print Preview in action.

Multi Purpose
From rapid prototypes and custom effects to printable output, SimRip offers several unique features for the screen print artist.

Introducing YRGBK 2.3

Hi, I’m back, and am happy to bring you the latest updates to my color separation tools for Adobe Photoshop®.

With a major redesign of the main panel, core advances and fixes, the new version of YRGBK provides easier access to advanced options with improved performance and accuracy.

The redesigned interface puts the most common color separation adjustments in the first window, making the process more intuitive and manageable.


The Black, White and Gray sliders control how far into the colors the values print.  (These are the saturation mask settings from the last version) The values now go from 0 to 100, with higher values increasing the amount of overprint.

The Four color sliders provide control over the Density and Saturation, as well as the amount of color in Shadow and Highlight areas. Checking the Black, White, Color or Gray boxes opens the advanced settings for that option.


The Advanced options in the secondary dialogs have been retooled as well, with more control and new adjustments. The new Black Generator offers more control over the Saturation mask as well as custom color sliders to fine tune the adjustment.

The Black generator with the new customized Saturation Mask.
The Black generator with the new customized Saturation Mask.

The new White scripts provide curve values and custom color adjustments all using convenient sliders.


The White generator curve and the custom color Mask.
The White generator curve and the custom color Mask.
The Base generator curve and the custom color Mask.
The Base generator curve and the custom color Mask.

The Color Generators New Transition Mask manages the mixing between colors for smoother transitions and softer blends. The Midtone adjustment and the Auto Option have been added as well, improving the fidelity of the image and the flexibility of the script.


The color generator and the custom color Mask.
The color generator and the custom color Mask.

Finally, the Gray Ramp is moved to a Gray dialog, which only displays when the Gray or Gray Component are being generated.


The Gray Ramp
The Gray Ramp

Between the main window controls and the advanced options windows, all the major variables in the color separation process can be adjusted.

You can read more about it here:

https://www.photoscreenprint.com/tutorials/yrgbk-manual/

https://www.photoscreenprint.com/download/yrgbk-color-separation-software/

It’s been an exciting process developing a script that offers quality and control up to my highest  standards. I am thankful to my many patient and generous supporters and sponsors.

Color Separations for Screen Printing