Sign & Digital Graphics

February '18

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S I G N & D I G I T A L G R A P H I C S • February 2018 • 45 Figure 7: Open an image that has natural perspec- tive. Figure 8: Duplicate the background layer name the layer "red" 3D. Anaglyphic 3D is used for scientific images for medical and anatomy books where depth perception is critical (see Figure 4). NASA images, including pic- tures from the Mars Rover, have been processed using anaglyphic 3D (see Figure 5). Other applications include geological illustrations by the United States Geological Survey and objects from various online museum objects… and let's not forget comic books and the most fun application of all—3 D under- wear (see Figure 6). RGB The anaglyphic technique can be used on full-color RGB and grayscale images that have been converted to RGB color mode. It works best on images that do not contain areas of pure and solid red such as solid-colored type, for example, because when the red areas are offset, the absence of the green and blue in the color channels produces little or no effect. Stereo Pair The most accurate anaglyphs are made with two cameras set a short dis- tance apart called a stereo pair. A stereo pair is two images of the same scene taken from slightly different perspec- tives at the same time. Objects closer to the cameras have greater differences in appearance and position within the image frames than objects further from the camera. The red channel from the left camera is combined with the green and blue channel of the right. Having been taken from a different angle, the red channel is naturally offset. Many computer graphics programs provide features that manipulate and combine individual color channels to prepare anaglyphs from stereo pairs. In practice, the left eye image is filtered to remove blue and green. The right eye image is filtered to remove red. The two images are usually positioned in the com- positing phase in close overlay registra- tion. Dedicated anaglyphic 3 D software is available that makes quick and simple work of combining channel information. Creating Anaglyphs A single image can also be made to look three-dimensional by moving the red channel to the left. The further it is moved, the stronger the 3D effect is. If this is done in stages, areas of the image will appear to recede into the distance to lesser or greater degrees. I present here two single image methods that you can use to create your own anaglyphic pictures. Bear in mind that there are many variations to these techniques that produce similar results. I've chosen these two relatively simple techniques because they don't require a great deal of knowledge of the software so that you can get started right away. In this demonstration I'm using Adobe Photoshop Creative Cloud, 2015. Two-Level 3D images This technique demonstrates the basics of advanced blending. Using this technique, you can create images with three, four or even more levels of depth. Choose an image with natural perspec- tive to enhance the effect. In this first example you'll create two levels of depth on a black and white image. In the second example I'll demonstrate how you can create continuous depth on a full-color image. Of course you'll need anaglyphic 3 D glasses to see the results. Open an image that has natural per- spective, and make any color, tonal, size, or content adjustments that are necessary (see Figure 7). If the image is a grayscale, convert it to RGB mode (Image > Mode > RGB). If the image is layered, choose Layer > Flatten Image. Duplicate the background layer name the layer "red," as in Figure 8. Double click the red layer to display the Layer Styles dialog box. Uncheck the red channel box and click OK (see Figure 9).

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