The Hidden Power of Photoshop CS: Chapter 2: Color Separations. Pt. 2. By Sybex | 4
The Hidden Power of Photoshop CS: Chapter 2: Color Separations. Pt. 2
This next set of steps continues from the previous. Screening each ink layer by the color components (C, M, and Y) isolates information for the ink while simultaneously creating a preview for the color. This state of the separation is temporary. To make this a really useful separation, you’ll have to convert the separated information to grayscale:
Figure 2.26 With this setup, you are all ready to separate the CMY colors.
1. Activate the Yellow layer.
2. Create a new layer choosing Use Previous Layer To Create Clipping Mask and call it Yellow Fill.
3. Fill the layer with pure blue (0, 0, 255 in RGB), and change the mode of the layer to Screen.
Figure 2.27 The basic RGB-CMY separation setup
4. Invert the layer (Image ‘ Adjustments ‘ Invert, or press z/Ctrl+I).
5. Activate the Magenta layer.
6. Create a new layer by choosing Use Previous Layer To Create Clipping Mask and call it Magenta Fill.
7. Fill the layer with pure green (0, 255, 0 in RGB). Change the mode of the layer to Screen.
8. Invert the Magenta Fill layer.
9. Activate the Cyan layer.
10. Create a new layer by choosing Use Previous Layer To Create Clipping Mask and call it Cyan Fill.
11. Fill the layer with pure red (255, 0, 0 in RGB).
12. Change the mode of the layer to Screen.
13. Invert the layer.
You can run through these steps manually or by running the CMYK Color action in the Hidden Power Tools.
If you complete these steps without a hitch, you’ll be looking at the same image you started with and the layers will look like Figure 2.27. If you shut off any two of the three color plate layers (e.g., Cyan and Yellow), you’ll see the separation named in the remaining layer (Magenta).
To make a viable separation, you have to convert the color layers to include grayscale representations of a color as tone.
Converting Color to Tone
Continuing on, the following steps adjust each layer to display tone only. You have to merge the filter with the channel to isolate the color and then neutralize layer color to isolate the tone.
1. Activate the Cyan Fill layer.
2. Press z/Ctrl+E to merge the fill with the Cyan layer.
3. Make a Hue/Saturation adjustment by choosing Image ‘ Adjustments ‘ Hue/Saturation. Choose Cyans from the Edit drop-down list, and move the Saturation and Lightness sliders all the way to the left (see Figure 2.28). This removes the color from the Cyan layer to make the Cyan tone.
4. Activate the Magenta Fill layer.
5. Press z/Ctrl+E to merge the fill with the Magenta layer.
6. Make a Hue/Saturation adjustment by choosing Image ‘ Adjustments ‘ Hue/Saturation. Choose Magentas from the Edit drop-down list, and move the Lightness sliders all the way to the left. This shifts the color from the Magenta layer to grayscale to make the Magenta tone.
7. Activate the Yellow Fill layer.
8. Press z/Ctrl+E to merge the fill with the Yellow layer.
9. Make a Hue/Saturation adjustment by choosing Image ‘ Adjustments ‘ Hue/Saturation. Choose Yellows from the Edit drop-down list, and move the Saturation and Lightness sliders all the way to the left. This removes the color from the Yellow layer to make the Yellow tone.
These steps commit the changes to the layers so that the layers are grayscale tone. They also remove the color, which means no preview is available. In the next set of steps, you will add the color back by reintroducing color screens to the plates. Running the CMYK Tone Seps action from the CD will complete the steps to neutralize the tone and add back the preview color (completing the steps from the next section).
Figure 2.28 The Hue/Saturation settings for changing the cyan separation to a grayscale cyan plate.
Reapplying Color for Previews
Follow the steps in the section “Separation” to add the preview color back (to do this independently, play the CMYK Color action in the Hidden Power Tools). The Layers palette should now look like Figure 2.29. See the color section for a preview of the CMY separation results.
Step 2: Handling the Black Separation
CMYK separation from RGB requires separation into CMY, and then generation of elements and masks to generate black (K). The way you handle implementation of black can vary depending on your preferences. We’ll look at one style that should help you understand the idea behind the process.
Figure 2.29 A complete CMY color separation should look like this with all the layers.
Now that you have the base plates, the black separation can be based on color saturation (or lack of) and luminosity (the darker portion of the image). These steps continue from completion of the basic separation in the previous section.
To complete black separation, you’ll have to know how to create saturation and luminosity masks. Both of these sources come from a luminosity and color separation, which mimics some of the properties of Lab mode in maintaining color information separate from tone.
This exercise should give you a hint as to the complexity of adjusting CMY for printed output, but it also offers you the opportunity to see inside the process and concepts behind how black is generated and how it is targeted to optimize print results.
Making the Saturation Mask
Creating a saturation mask allows you to target gray areas of the image and replace the purer grays with black rather than a CMY mix, which can shift hues depending on their mixture. Follow these steps:
Figure 2.30 This setup is the basic luminosity and color separation. You can use this in different ways to adjust the black result.
1. Duplicate your background image to another document by choosing Duplicate Layer from the Layers palette pop-up menu. Choose New as a Document Destination in the Duplicate Layer dialog box. This opens the background in a new image.
2. Duplicate the background two times. Change both the name and mode of one of the duplicates to Luminosity, and change the other duplicate’s name and mode to Color.
3. Activate the background layer, create a new layer called Composite, and fill with 50 percent gray (RGB 128, 128, 128). At this point, the layers should look like they do in Figure 2.30.
4. Shut off the view for the Luminosity layer and move it to the top of the layer stack (if it is not there already).
5. Duplicate the Composite layer.
6. Merge the Color layer with the Composite Copy. You can do this by activating the Color layer and pressing F/Ctrl+E. This commits existing color.
7. Set the layer mode to DifferenceThe image now appears brighter in areas where there was more saturated color. Merge that layer with the Composite layer to commit the result.
8. Open Hue/Saturation. Set Saturation to –100%. This will neutralize the color.
9. Open the Levels dialog box by pressing z/Ctrl+L. Set the sliders to adjust tonality by moving the white slider to 128. This adjustment can vary depending on the image and on what you want to accomplish and how you want to affect the separation. Setting the slider to 128 will exclude light and fully saturated colors from containing additional black. Making a stronger change will eliminate a greater portion of saturated color and confine black generation to less saturated areas. Making a lesser change will include saturated color in black generation. Name the layer Saturation.
At this point you will have a saturation mask. It should look something like Figure 2.31. It represents a mapping of color in the image from most saturated (lightest) to least (darkest).
Figure 2.31 The saturation mask shows lighter in areas where the color is most pure (has the least gray).
Created: March 27, 2003
Revised: March 1, 2004
URL: URL: http://webreference.com/graphics/ps2/1