Designs with a Difference

SAN FRANCISCO (03/28/2000) - You can get startling, even psychedelic effects in Adobe Systems Inc.'s Photoshop by using that program's blending modes, which determine how color information on two different layers interacts when you combine the layers. Some blending modes-like the aptly named Normal-produce fairly ordinary results, while others give you a radically changed image. One of the most popular is Difference mode, which produces highly saturated color.

The problem with using such a popular mode, though, is that its effects are so predictable, they're easy to spot in an illustration.

Graphic designer and photo-illustrator Alicia Buelow is an ardent fan of Difference mode, but she doesn't like the idea of using a one-effect-fits-all mode, as it's likely to make her illustrations look too much like someone else's. And while she appreciates the dramatic effects this mode provides, she doesn't like what she considers its colorful excesses. She gravitates toward a palette of earth tones rather than the intense blues and greens characteristic of Difference. Fortunately, Buelow found a way to make Difference behave differently. She devised a technique involving copying and pasting images that lets her tone down the mode's effect (see Step 4).

Buelow designed Ascendence as a self-promotional piece, using Photoshop 5.5 on a 333MHz Power Mac G3 with 256MB of RAM. She's a former Adobe employee who has worked with Photoshop and Illustrator since the early days of both programs.

CATHY ABES, author of Photoshop F/X (Ventana Press, 1994) and formerly an editor at Macworld and Publish, has been writing about graphics and publishing for more than ten years.

A Subtler Difference

After creating a background, Buelow pieced together the crow image from three photos (two of her own and one stock photo) and added it to a layer on top of the background. She made the crow image a single color by selecting Colorize in the Hue/Saturation dialog box. To make the crow blue so it would stand out against the brownish gold background, she moved the Hue slider about half-way to the right.

Buelow inverted the crow layer (Image: Adjust: Invert) and then applied Difference blending mode at 100 percent opacity. Inverting the crow image before applying Difference mode produced a more dramatic effect than if she had used Difference mode alone.

The next step was to get a psychedelic effect that she could later tone down.

To do so, Buelow selected the crow layer, duplicated it, and merged the duplicate and the original with both layers set on Difference blending mode. As she expected, the result was an overly saturated and unnatural-looking bird, but one with some desirable effects.

Once you set a layer to Difference mode, you can't get rid of the saturated colors without losing the high-contrast effect. Buelow devised a way to work around that limitation. To begin, she saved a copy of the image as a flattened Photoshop file by checking the Flatten Image check box in the Save A Copy dialog box. With the layered image still open, Buelow opened the flattened image and selected the crow by going back to the layered image, choosing the marquee tool, and command-clicking on the icon of one of the crow layers. Then she clicked inside her selection with the marquee tool and dragged the selection over the crow in the flattened image. When she let go, the crow in the flattened image was automatically selected. Finally, she copied and pasted the crow from the flattened image into the layered image.

Now that Buelow had an image that looked like it was in Difference mode but was actually in Normal mode, she could select that image's layer and adjust colors (in the Hue/Saturation dialog box) without losing the high-contrast effect.

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