Why Two Grain Filters?

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Why does Photoshop include two filters called Film Grain and Grain, rather than one? In practice, each operates a little differently than the other, producing different effects, but we can thank the free enterprise system for their existence. Photoshop's current Film Grain filter was originally part of a third-party set of 16 compatible plug-ins called Aldus Gallery Effects, which sold for $199. These filters proved so successful that Aldus Corporation followed up with a second set of 16, which included the slightly different Grain filter. Soon after Aldus released the third Gallery Effects library, Adobe acquired the company (adding PageMaker to its product line along with Gallery Effects). The filters were sold by Adobe for a time, but disappeared as a separate product when they were folded into Photoshop 4.0.

Add Noise

The Add Noise filter (Filter > Noise > Add Noise) has one slider, a pair of radio buttons, and a checkbox. You can select an Amount from 1 to 999 (the default value is 32). This value is used to determine how much the random colors added to the selection will vary from the color that is already present (or from the gray tones, if you're working with a monochrome image).

Choose either Uniform or Gaussian distribution of the noise. Uniform distribution uses random numbers in the range from 0 to the number you specified with the Amount slider. The random number is then added to the color value of the pixel to arrive at the noise amount for that pixel. Gaussian distribution uses a bell-shaped curve calculated from the values of the pixels in the selected area, producing a more pronounced speckling effect.

Mark the Monochromatic box to apply the noise only to the brightness/darkness elements of the image without modifying the colors themselves. This can reduce the "color specks" effect that often results from applying noise to a color image.

Mezzotint

The Mezzotint filter (Filter > Pixelate > Mezzotint) is another technique borrowed from traditional printing, in which a special overlay is placed on top of a photograph to add a pattern during duplication. Digital filters offer much the same effect with a little less flexibility, since the range of mezzotints you can achieve with Photoshop is fairly limited. Only dots (fine, medium, grainy, or coarse), lines, or strokes (in short, medium, and long varieties) can be applied. You can rotate your image, apply this filter, and then rotate it back to the original orientation if you want to change the direction of the lines or strokes.

Figure 3.32 shows examples of grain effects produced by the Film Grain, Grain, Add Noise, and Mezzotint filters.

Figure 3.32. Various film grain effects. In the top row (left to right), the original image; Film Grain filter with Grain, Highlight Area, and Intensity all set to values of 5; Film Grain filter with settings of 10, 5, and 7. In the bottom row (left to right), Grain filter set to Speckle; Add Noise filter; and Mezzotint filter in Fine Dots mode, then faded to reduce the effect slightly.

Figure 3.32. Various film grain effects. In the top row (left to right), the original image; Film Grain filter with Grain, Highlight Area, and Intensity all set to values of 5; Film Grain filter with settings of 10, 5, and 7. In the bottom row (left to right), Grain filter set to Speckle; Add Noise filter; and Mezzotint filter in Fine Dots mode, then faded to reduce the effect slightly.

Diffuse Glow

Thisdocumentiscreatedwith trialversion ofCHM2PDFPilot2.16.100. which can produce a radiant luminescence in any image. The glow seems to suffuse from the subject and fill the picture with a wonderful luster, while softening harsh details. It's great for romantic portraits, or for lending a fantasy air to landscapes. Diffuse Glow works equally well with color and black-and-white images, using the dialog box controls shown in Figure 3.33.

Figure 3.33. The Diffuse Glow dialog box lets you control the amount of Grain, Glow, and Clear areas in your image.

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Figure 3.33. The Diffuse Glow dialog box lets you control the amount of Grain, Glow, and Clear areas in your image.

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You can get a variety of effects by manipulating the filter's controls, such as the examples shown in Figure 3.34. The Graininess slider adds or reduces the amount of grain applied to an image. A large amount obscures unwanted detail and adds to the dreamy look of the image. The Glow Amount control adjusts the strength of the glow, as if you were turning up the voltage on a light source. The higher the setting, the more glow is spread throughout your picture. The Clear Amount slider controls the size of the area in the image that is not affected by the glow. You can use this control with the Glow Amount slider to simultaneously specify how strong a glow effect is produced, as well as how much of the image is illuminated by it. The current background color becomes the color of the glow. That's an important point. Beginners sometimes forget this, and then wonder why their glow effect looks weird. If you want a glowing white effect, make sure the background color is white. Anything else will tint your image. You can use this feature to good advantage, by selecting background colors with a very slight tint of yellow, gold, or red to add a sunny or warm glow to your image.

Figure 3.34. The original photo (top left) with three variations on the Diffuse Glow filter.

Figure 3.34. The original photo (top left) with three variations on the Diffuse Glow filter.

In the examples, the portrait in the upper right has the Graininess control set to 5, the Glow Amount control set to 10, and the Clear amount set to 20. At lower left the diffusion is less obvious, and the contrast not quite as high, producing a romantic fuzziness that doesn't take over the entire picture. I used Graininess, Glow amount, and Clear amount settings of 1, 4, and 12, respectively. Finally, for the example in the lower right I concentrated the attention on the model's eyes by using settings of 7, 10, and 15, and then merged the layer with a copy of the original, unmodified layer, using the Layer palette's Merge drop-down list set to Lighten. In that mode, Photoshop looks at each pixel in the two layers and uses the lightest pixel for the final image. The resulting picture is very washed out and grainy with an interesting high-contrast appearance.

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