Oreilly Photoshop CS5 The Missing Manual_2 ppt

215  :     Basic Channel Stunts Note: What’s the difference between “noise” and “grain”? They both describe tiny flecks on your image, but, technically speaking, noise occurs in digital images, whereas grain occurs in analog prints, film, and transparencies. In other words, grain becomes noise once you scan the image. However, let’s say you’re in RGB mode and you dutifully followed the instructions on page 462 and ran the Reduce Noise filter on your blue channel (which typically has the most noise, though sometimes noise can hide out in the red channel) and it didn’t do squat. What do you do? You can try bringing out some of the details in your image by sharpening only the red and green channels, as shown in Figure 5-15. Figure 5-14: Photoshop doesn’t let you merge two channels into one, but you can combine them into a new channel with the Calculations command: Choose Image➝Calculations and, in the dialog box shown here, set the Source 1 section’s Channel pop-up menu to “Red copy” and the Source 2 section’s menu to “Green copy”. Choose Multiply from the Blending pop-up menu at the bottom of the dialog box if you want to create a black object or Screen if you want to create a white one. When everything’s set, click OK. 216 P CS: T M M Basic Channel Stunts Tip: The next time you need to sharpen a portrait of someone who’s sensitive about his or her appear- ance, try sharpening only the red channel to avoid bringing out unwanted details in the person’s skin. (As you learned earlier in this chapter, most of the fine details live in the high-contrast green channel.) Here’s how to sharpen without making noise any worse than it already is: 1. Open your image and make a copy of the layer(s) you’re going to sharpen. If you’re working with a document that has just one layer, select it in your Layers panel and duplicate it by pressing �-J (Ctrl+J on a PC). If you like, double-click the layer’s name and rename it Sharpen. If you’re working on a multilayer document, press and hold the Option key (Alt on a PC) while choosing Merge Visible from the Layers panel’s menu (see the figure on page 78). Photoshop combines all the layers into a new layer. Drag this new layer to the top of your Layers panel and name it Sharpen. Figure 5-15: If you select the red and green channels before running a sharpening filter, you restrict the sharpening to those channels. That helps you avoid sharpening, and therefore accentuating, any noise. 2. Open the Channels panel (page 189) and select the red and green channels. Click to select one channel and then Shift-click to select the other one, so they’re both highlighted in your Channels panel. Don’t panic if your image turns a weird color (like the horse in Figure 5-15); Photoshop is just showing you the image using only those two color channels. 217  :     Basic Channel Stunts 3. Choose Filter➝Sharpen➝Unsharp Mask (page 463). When you run a filter while you’ve got only certain channels selected, Photo- shop applies the sharpening to just those channels. In this case, it won’t apply any sharpening to the blue channel. Click OK to close the Unsharp Mask dialog box. 4. In the Channels panel, turn on the composite channel (here, that’s RGB) to see your new and improved full-color image. You’re done! If you want to see before and after versions of your image, open the Layers panel and toggle the Sharpen layer’s visibility eye (page 82) off and on. Tip: Another, more advanced way to sharpen your image is to use the channel with the highest contrast to create an intricate edge mask. You can read all about that process on page 475. [...]... in the same way, the steps are almost identical Just open the images in Camera Raw by selecting them in Bridge or Mini Bridge (see Appendix C, online) or simply by finding them on your hard drive and opening them from there When the thumbnails appear in the filmstrip on the left side of the Camera Raw window, click the Select All button and then use the Crop tool as described in this section All the. .. weren’t originally there through a mathematical process called interpolation, in which it uses the pixels that are there to guess what the new ones should look like The options below the Resample Image checkbox determine which kind of mathematical voodoo Photoshop uses to either add or delete pixels Since better image quality means more work for Photoshop, the better the image, the more time Photoshop takes... increasing the size by 900 percent all at once) Here’s what you do: Open the Image Size dialog box, make sure both the Resample Image checkbox and the Constrained Proportions checkbox at the bottom of the dialog box are turned on, and then choose Bicubic Smoother from the method pop-up menu Then, in the dialog box’s Document Size section, change either the Width or Height pop-up menu to Percent 244 (the other... having Photoshop crop, straighten, and split them into separate files for you—all with the flick of a single menu command With the page of photos open, choose File➝Automate➝“Crop and Straighten Photos” Photoshop instantly calculates the angle of the overall image’s edge (that is, the edge of the photo bits) against the white background, rotates the images, and then duplicates all the photos into their... it below the original photo layer At the bottom of the Layers panel, click the new layer icon (it looks like a piece of paper with a folded corner) To keep from covering up the whole photo in the next step, drag the new layer’s thumbnail below the original layer Alternatively, you can ⌘-click (Ctrl-click) the icon to make Photoshop add the new layer below the currently active layer 5 Fill the new layer... resurrect them later (see Figure 6-13 for details) • The Open Images button to apply the changes and open the photo(s) in Photoshop 234 Photoshop CS5: The Missing Manual Cropping Images Figure 6-12:  Open one or more images in Camera Raw and use the Crop tool just like you would in Photoshop (Remember, Camera Raw is actually a separate program.) Simply drag across the image to draw a box and then press... photos, and that’s the format selected in the figure.) 248 Photoshop CS5: The Missing Manual Resizing Images 3 To keep the photo’s quality relatively intact while you reduce the file size, choose High from the Compression Quality pop-up menu (also circled in Figure 6-20, upper right) To make the file smaller, Photoshop throws away image details and then compresses what’s left If you set the quality level... pixels), they’re just smaller because they’re packed more tightly together (they have a higher resolution) in the confines of the measuring cup (the Photoshop document) The loosely packed granules you started with are like low resolution, and the firmly packed granules are like high resolution (Hungry yet?) Since increasing image resolution—from, say, 72 ppi to 300 ppi—makes the pixels smaller and packs them... can leave them a bit distorted, as shown here To crop with perspective, first draw a crop box around the object you want to straighten (The box doesn’t have to be exactly aligned with the object, but you do want to grab the whole object.) Next, turn on the Perspective checkbox in the Options bar and then drag the corner handles so the lines of the crop box are parallel to (or on top of) the angled... reflect the size of the crop box as you draw • Cancel to exit Camera Raw without applying the changes • Done to apply the changes (which you can edit the next time you open the image in Camera Raw) and exit the Camera Raw window Tip: You can use keyboard shortcuts to change how the Save, Open, Cancel, and Done buttons at the bottom of the Camera Raw window behave: To open a copy of the image in Photoshop . Photos”. Photoshop instantly calculates the angle of the overall image’s edge (that is, the edge of the photo bits) against the white background, rotates the images, and then duplicates all the. hard drive and opening them from there. When the thumbnails appear in the filmstrip on the left side of the Camera Raw window, click the Select All button and then use the Crop tool as described. the whole photo in the next step, drag the new layer’s thumbnail below the original layer. Alternatively, you can ⌘-click (Ctrl-click) the icon to make Photoshop add the new layer be- low the