Capturing Color Images

Today we have several options for capturing images for manipulation in Photoshop. Color scanners have been around the longest, for around 50 years, in fact. The first ones I saw early in my career cost more than a million dollars when you included the computer equipment needed to drive them, and they were intended only for professional graphics applications at service bureaus and large publications. Today, color scanners, like the one shown in Figure 6.9, can cost less than $100.

Figure 6.9. Modern color scanners can cost $100 or less.

Figure 6.9. Modern color scanners can cost $100 or less.

Color scanners are nothing more than a system for capturing the proper amount of each of the primary colors of light in a given image. So, these scanners use three different light sourcesone each of red, green, and blueto scan a color image. To do so, some older scanners actually made three passes over the imageonce for each color. More recent scanners use multiple light sources, or "rotate" their illumination, using red/green/blue light in succession to capture an image in a single pass.

The amount of light reflected by the artwork for each color varies according to the color of the pigments in the original. Cyan pigment, for example, absorbs red light and reflects blue and green. So, when a cyan area is illuminated by the red fluorescent light in a scanner, relatively little light is reflected. Most of the light produced by the blue and green fluorescents is reflected. Your scanner software records that area of the original as cyan. A similar process captures the other colors in your subject during the scan. Even if you don't use a scanner yourself, you may work with scanned images that are captured by your photofinisher when converting your color slides or prints to digital form for distribution online or as a PhotoCD or Picture CD.

Digital cameras cut out the middle step by creating color images directly. Where scanners use a linear array that grabs an image one line at a time, digital cameras use a two-dimensional array that grabs a complete bitmap in one instant. Today, digital cameras with 3.3 to 6 megapixels (or more) of resolution can capture images that are virtually indistinguishable from those grabbed on film when reproduced or enlarged to 8 x 10 inches or less.

You'll find more information about color scanners in my book Mastering Digital Scanning with Slides, Film, and Transparencies (ISBN: 1-59200-141-6) and lots more nuts-and-bolts on digital cameras in Mastering Digital Photography (ISBN: 1-59200-114-9). If you want to learn how digital cameras capture color, check out Mastering Digital Photography or Mastering Digital SLR Photography. All three books are available from Course Technology, and you can find more information about them at my website, www.dbusch.com.

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