Photoshop CS4 Studio Techniques- P13

Photoshop CS4 Studio Techniques- P13: Staring at a shelf full of Photoshop books at the localbookstore, it seems that there are more special-effect“cookbooks” and technical tomes than anyone would evercare to read. The problem is that none of those “cookbooks”provide enough detail to really let you feel like youunderstand the program
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Photoshop CS4 Studio Techniques- P13Chapter 9 Enhancements and Masking Unlike the Background Eraser, which truly deletes the background of the image, the Blending sliders temporar- ily hide areas. You can move the sliders to their default locations to reveal the areas that were being hidden by the sliders. To delete the hidden areas, Command/Ctrl-click the New Layer icon at the bottom of the Layers panel to create a new layer below the one that has the sliders applied. Click the layer above the one you just created, making the slider-applied layer active. Finally, choose If you used the Blending sliders to Layer > Merge Down, and the slider-applied layer will be hide the background, be sure to combined with the empty layer. Because the underlying convert the result into a permanent layer didn’t have the sliders applied, Photoshop will be deletion before attempting to convert it into a layer mask. forced to retain the look of the slider-applied layer without actually using the sliders. Channels In older versions of Photoshop, you used channels to iso- late complex images from their backgrounds. These days, you’ll mainly use channels with simpler images, especially when working with an illustration instead of a photo- graphic image. Often, you can convert images into spot colors so that each color in the image prints with a differ- ent color of ink (instead of printing with standard CMYK inks). Channels are the subject of one of the bonus videos on the book’s website (www.danablan.com/photoshop), but for the moment let’s look at how to use the Channels panel to isolate each color within an image. This might seem cumbersome at first, but read on and you’ll see the value of this approach. Let’s say you have a logo or graphic that you’d like to reproduce on a commercial printing press using red, blue, and yellow ink. You should look at the original and decide which areas will use each ink and if any areas need a com- bination of more than one ink. In Figure 9.129, it’s rather obvious which areas should use red and blue ink, but maybe you’d like to use a combination of yellow and red to Figure 9.129 The example image, a crunchy bag of potato chips. (©2007 make up the potato chips in this shot. To determine which PhotoSpin, www.photospin.com.) channels you’ll need, click through all the channels in the346 IV: Creative TechniquesChannels panel and look for good contrast between thecolor you’re attempting to isolate and whatever surroundsit (Figure 9.130). In this example, you’ll use the red chan-nel to isolate the blue areas, the blue channel to isolate thered areas, and a combination of the red and blue channelsfor the potato chips.Figure 9.130 Left to right: red channel, green channel, blue channel.To isolate the blues, drag the red channel to the NewChannel icon at the bottom of the Channels panel. (Itlooks like a sheet of paper with the corner folded over.)Next you need to isolate the area that should print withblue ink; if you make it black, the surrounding areasshould end up white to indicate that no blue ink will beused. Choose Image > Adjustments > Levels, click the blackeyedropper, and then click ...