Photoshop 6 for Windows Bible- P13

Photoshop 6 for Windows Bible- P13:If you are reading this foreword, it probably means that you’ve purchased a copyof Adobe Photoshop 6.0, and for that I and the rest of the Photoshop team atAdobe thank you.If you own a previous edition of the Photoshop Bible, you probably know what toexpect. If not, then get ready for an interesting trip.
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Photoshop 6 for Windows Bible- P13 Chapter 8 ✦ Selections and Paths 329 32 (default) 60 100Figure 8-6: Note the results of clicking on a pixel with a brightnessvalue of 140 (top row) and a brightness value of 10 (bottom row)with the tolerance set to three different values. Red Green BlueFigure 8-7: Because the yellow Sasquatch sign contains almost no blue, it appearsmost clearly distinguished from its background in the blue channel. So the bluechannel is the easiest channel in which to select the sign with the magic wand.330 Part III ✦ Selections, Masks, and Filters Note Here’s one more twist to the Tolerance story: The magic wand is affected by the Sample Size option that you select for the eyedropper tool. If you select Point Sample, the wand bases its selection solely on the single pixel that you click. But if you select 3 by 3 Average or 5 by 5 Average, the wand takes into account 15 or 25 pixels, respectively. As you can imagine, this option can have a noticeable impact on the extent of the selection that you get from the wand. Try clicking the same spot in your image using each of these Sample Size settings, using the same Tolerance value throughout, to see what I mean. Making the wand see beyond a single layer The Use All Layers option enables you to create a selection based on pixels from different layers (see Chapter 12 for more about layers). Returning to my previous landmass example, suppose you set Europe on one layer and North America on the layer behind it so the two continents overlap. Normally, if you clicked inside Europe with the magic wand, it would select an area inside Europe without extending out into the area occupied by North America on the other layer. Because the wand doesn’t even see the contents of other layers, anything outside Europe is an empty void. We’re talking pre-Columbus Europe here. If you select Use All Layers, though, the situation changes. Suddenly, the wand can see all the layers you can see. If you click on Europe, and if North America and Europe contain similar colors, the wand selects across both shapes. Mind you, while the Use All Layers option enables the wand to consider pixels on different layers when creating a selection, it does not permit the wand to actually select images on two separate layers. Strange as this may sound, no selection tool can pull off this feat. Every one of the techniques explained in this chapter is appli- cable to only a single layer at a time. Use All Layers merely allows the wand to draw selection outlines that appear to encompass colors on many layers. What good is this? Well, suppose you want to apply an effect to both Europe and North America. With the help of Use All Layers, you can draw a selection outline that encompasses both continents. After you apply the effect to Europe, you can switch to the North America layer — the selection outline remains intact — and then reapply the effect. Ways to Change Selection Outlines If you don’t draw a selection outline correctly the first time, you have two options. You can either draw it again from scratch, which is a real bore, or you can change your botched selection outline, which is likely to be the more efficient solution. Chapter 8 ✦ Selections and Paths 331 You can deselect a selection, add to a selection, subtract from a selection, and even select the stuff that’s not selected and deselect the stuff that is. (If this sounds like a load of nonsense, keep reading.) Quick changes Some methods of adjusting a selection outline are automatic: You choose a com- mand and you’re finished. The following list explains how a few commands — all members of the Select menu — work: ✦ Deselect (Ctrl+D): You can deselect the selected portion of an image in three ways. You can select a different portion of the image; click anywhere in the image window with the rectangular marquee tool, the elliptical marquee tool, or the lasso tool; or choose Select ➪ Deselect. Remember, though, when no part of an image is selected, the entire image is susceptible to your changes. If you apply a filter, choose a color-correction command, or use a paint tool, ...