Photoshop.CS.Bible [Electronic resources] نسخه متنی

Brush Modes

When certain painting or editing tools are active, the Options bar provides access to Photoshop's brush modes, which control how the colors applied by the tool mix with existing colors inside an image or layer. Figure 5-33 shows which brush modes are available when you select various tools.

Figure 5-33: The specific Mode settings in the Options bar vary depending on which tool is active. The Mode pop-up menu changes to Range when using the dodge or burn tool.

With the exception of the specialized modes available for the dodge, burn, and sponge tools, these brush modes are merely variations on the blend modes available in the Layers palette, which I examine in Chapter 13. The difference is that the blend modes in the Layers palette mix colors between layers but the brush modes in the Options bar mix colors inside a single layer. Because of this subtle distinction, I describe the modes twice, once in the following section and again in Chapter 13. The latter discussion is more detailed, so if you don't get all the info you need here, feel free to read Chapter 13 to find out more.

The 25 paint tool modes

Photoshop CS offers a total of 25 brush modes when you use the brush, the pencil, or any of the other tools shown along the left side of Color Plate 5-3 shows a representative from each group, as applied to the strokes I drew by Shift-clicking with the brush tool way back in Figure 5-5. I also varied the Opacity settings to achieve what I considered to be optimal results.

Normal (N): Choose this mode to paint or edit an image normally. A paint tool coats the image with the foreground color, and an edit tool manipulates the existing colors in an image according to the Opacity, Strength, Flow, and Exposure values.

Two color modes prevent Photoshop from rendering soft or translucent edges. The black-and-white and indexed modes (Image Mode Bitmap and Image Mode Indexed Color) simply don't have enough colors to go around. When painting in such a low-color image, Photoshop replaces the Normal brush mode with Threshold (L), which results in harsh, jagged edges, just like a stroke painted with the pencil tool. You can alternatively dither the soft edges by selecting the Dissolve mode, as described next.

Dissolve (I): Dissolve scatters a random pattern of colors to simulate translucency. The pattern shows up along the edges of opaque brushstrokes or inside translucent strokes, like those in Figure 5-34. Note that this mode and the two that follow are not applicable to the edit tools. To get something resembling Dissolve with, say, the smudge tool, try applying the Noise setting in the Brushes palette.

Figure 5-34: Lines painted with the Normal (left) and Dissolve (middle) mode set to 50 percent opacity. Dissolve dithers colors to simulate translucency, as the magnified detail shows (right).

Behind (Q): This mode is applicable exclusively to layers with transparency. When Behind is selected, the paint tools apply color behind the image on the active layer, showing through only in the transparent and translucent areas. Figure 5-5 by applying each coat of lighter color behind the last. Note that when working on an image without layers or on the background layer of a multilayered image, the Behind mode is dimmed.

Figure 5-35: To build up the layers of color in this painting, I drew the darkest colors first and then applied progressively lighter colors using the brush tool set to the Behind mode.

Clear (R): When working on a layer other than Background, the Clear mode turns the brush, pencil, or paint bucket into an erasing tool, clearing away pixels. Given that the eraser already emulates the behavior of both the brush and pencil tools (as I explain in Chapter 7), there's not a lot of reason to use Clear with either of these tools. However, it creates a unique effect when combined with the paint bucket, as explained in the next chapter.

Darken (K): The first of the four darkening modes, Darken applies a new color to a pixel only if that color is darker than the pixel's present color. Otherwise, the pixel is left unchanged. The mode works on a channel-by-channel basis, so it might change a pixel in the green channel, for example, without changing the pixel in the red or blue channel.

Multiply (M): The Multiply mode combines the foreground color with an existing color in an image to create a third color, darker than the other two. Using the multiply analogy, cyan times magenta is blue, magenta times yellow is red, yellow times cyan is green, and so on. Discussed in Chapter 4, this is the subtractive (CMYK) color theory at work. The effect is almost exactly like drawing with felt-tip markers, except the colors don't bleed. The second examples in Color Plate 5-3 show the Multiply mode in action.

Figure 5-36: Examples of three of the four darkening modes applied to grayscale versions of my Shift-click painting. In all cases, the Opacity setting is 100 percent.

Color Burn (B) and Linear Burn (A): The two Burn modes are designed to simulate colored versions of the burn tool. Typically (though not always), Color Burn results in a darker, more colorful stroke than Multiply. Linear Burn is darker still and more muted, as shown in the last example in Figure 5-36. When combined with low Opacity values, the two modes can be interesting, but I wouldn't go so far as to call them particularly helpful.

Lighten (G): Leading the lightening modes is the appropriately named Lighten, which ensures that Photoshop applies a new color to a pixel only if the color is lighter than the pixel's present color. See the first image in Color Plate 5-3 for examples.

Figure 5-37: Three of the four lightening modes. Note that Linear Dodge has a tendency to send a large portion of the colors to white. The same is true of Color Dodge as well.

Screen (S): The inverse of the Multiply mode, Screen combines the foreground color with each colored pixel you paint to create a third color, lighter than the other two. Red on green is yellow, green on blue is cyan, blue on red is magenta. In other words, Screen obeys the rules of the additive (RGB) color theory.

Color Dodge (D) and Linear Dodge (W): Intended to emulate the dodge tool, these modes radically lighten an image. Color Dodge produces the more colorful effect; Linear Dodge works out to be the lightest (see the last image in Figure 5-37 for an example). As with the Burn modes, you're likely to have the most luck with the two Dodge modes at low Opacity values.

Overlay (O): The seven modes starting with Overlay are cousins, each multiplying the dark pixels in an image and screening the light pixels. Of the seven, Overlay is the kindest and arguably the most useful. It enhances contrast and boosts the saturation of colors, rather like a colored version of the sponge tool set to Saturate. The first image in Figure 5-38 shows the Overlay mode in action.

Figure 5-38: The medium Overlay, subtle Soft Light, and extreme Linear Light modes each mix brushstrokes to darken the darkest colors in an image and lighten the lightest colors.

Soft Light (F) and Hard Light (H): The Soft Light mode applies a subtle glazing of color to an image. Even black or white applied at 100 percent Opacity does no more than darken or lighten the image, but it does slightly diminish contrast, as you can see in the middle image in Figure 5-38. Meanwhile, Hard Light produces a much stronger effect, even stronger than Overlay. Of the modes we've seen so far, only Normal is more opaque.

Vivid Light (V) and Linear Light (J):Color Plate 5-3 shows an example.) Linear Light produces an even higher contrast effect, as shown in the last image in Figure 5-38. Try one of these modes when you want to simultaneously burn the darkest colors in an image and dodge the lightest ones.

Pin Light (Z): This peculiar mode drops out all but the so-called "high frequency" colors, which are the lightest, darkest, and most saturated color values, as illustrated in the first example in Chapter 13.

Figure 5-39: The Pin Light mode preserves only high-frequency colors, making less vividly colored brushstrokes invisible. Difference and Exclusion modes subtract color values, resulting in colorful inversion effects.

PhoteshopHard Mix (L): This new mode paints using the Vivid Light brush mode and then applies a threshold operation to each color channel. The result is a stark, high-contrast mix consisting of only eight primary colors: red, green, blue, cyan, magenta, yellow, white, and black. For more information on thresholds, consult Chapter 17.

Difference (E): When a paint tool is set to the Difference mode, Photoshop subtracts the brightness value of the foreground color from the brightness value of the pixels in the image. If the result is a negative number, Photoshop simply makes it positive. The result of this complex-sounding operation is an inversion effect. Painting with black has no effect on an image; painting with white inverts it.

Exclusion (X): When I first asked Mark Hamburg, lead programmer for Photoshop, for his definition of Exclusion, he kindly explained, "Exclusion applies a probabilistic, fuzzy-set-theoretic, symmetric difference to each channel." Ouch, copying and pasting that text hurt my head. In any case, I'm not sure, but I think what he meant was that Exclusion inverts an image in much the same way as Difference, except colors in the middle of the spectrum mix to form lighter colors, as in the case of the second-to-last image in Color Plate 5-3.

Hue (U): Understanding this and the next few modes requires a color theory recap. Remember how the HSL color model calls for three color channels? One is for hue, the value that explains the colors in an image; the second is for saturation, which represents the intensity of the colors; and the third is for luminosity, which explains the lightness and darkness of colors. If you choose the Hue brush mode, therefore, Photoshop applies the hue from the foreground color without changing any saturation or luminosity values in the existing image.

Note that all HSL brush modes — Hue, Saturation, Color, and Luminosity — are exclusively applicable to color and are therefore unavailable when painting in grayscale images.

Saturation (T): If you choose this mode, Photoshop changes the intensity of the colors in an image without changing the colors themselves or the lightness and darkness of individual pixels.

Color (C): This mode combines Hue and Saturation to change the colors in an image and the intensity of those colors without changing the lightness and darkness of individual pixels.

Luminosity (Y): The opposite of the Color mode, Luminosity changes the lightness and darkness of pixels, but leaves the hue and saturation values unaffected. The final example in Color Plate 5-3 shows how I was able to use the Luminosity mode to trace lines and shadows without altering the color values in the original image.

The three dodge and burn modes

I've taken care of the brush modes available to the paint tools, the smudge tool, the color replacement tool, and the two focus tools. I explained the Desaturate and Saturate modes available to the sponge tool in the section "Mopping up with the sponge tool." That leaves the three brush modes available to the dodge and burn tools.

You access these modes from the Range pop-up menu in the Options bar. As with other brush modes, you can select the dodge and burn modes from the keyboard. Just press Shift+Alt (Win) or Shift-Option (Mac) and the letter in parentheses as follows:

Midtones (M): Selected by default, the Midtones mode applies the dodge or burn tool equally to all but the very lightest or darkest pixels in an image. Midtones enables you to adjust the brightness of colors without blowing out highlights or filling in shadows.

Shadows (S): When you select this mode, the dodge or burn tool affects dark pixels in an image more dramatically than light pixels. As illustrated in Figure 5-40, medium values are likewise affected, so the Shadows option modifies a wider range of colors than Midtones.

Figure 5-40: The dodge and burn tools applied at 100-percent Exposure settings subject to each of the three applicable brush modes.

Highlights (H): This option lets you lighten or darken the midtones and lightest colors in an image.

Selecting Shadows when using the dodge tool or Highlights when using the burn tool has an equalizing effect on an image. For example, the first brushstroke in Figure 5-40 shows the Shadows option combined with the dodge tool. As a result, Photoshop paints an almost consistent brightness value across the course of a white-to-black gradient. The same is true for the last brushstroke, which combines Highlights with the burn tool.