Color Depth
Scanner resolution differs from company to company. More important from a
color management standpoint, some scanners capture a broader range and depth
of color.
Color depth is a measurement of the amount of color information captured in each
pixel of a scan or digital capture. (A pixel, or “picture element,” is a single element
of an image. For the purposes here, it typically consists of red, green, and blue
color elements combined in varying amounts to render a desired color.)
The color depth captured by your scanner can make a big difference in your final
product. Sometimes described as bit depth, higher color depth provides better color
representation and gives you more “elbow room” in editing and manipulating colors.
Here are some examples:
? Consumer-level camera: 8 bits
? Prosumer camera: 8 bits or 12 bits
? Professional digital SLR: 12 bits
? Professional medium-format digital camera back: 16 bits
? Desktop dedicated film scanner: 14 bits
? Virtual drum, or drum scanner: 16 bits
These measurements might seem closer together than they really are. There is a
huge difference between an 8-bit image and a 16-bit image, because these numbers
are exponential.
A pixel that has a bit depth of 1 can be black or white. A pixel that has a bit depth
of 8 has 28 tones, which equals 256 tonal values.
A pixel with a bit depth of 16 is expressed as 216 and has 65,536 potential tonal
values.
Going further down this road and making the calculation for RGB or CMYK color
shows that we have billions and billions of possible tones (apologies to Carl Sagan).
It’s also true that current technology can’t display or print 100% of this range of
colors. However, it is important that you understand that higher bit depth images
give you the ability to manage or manipulate color more effectively and with
significantly less distortion of final product.
The gaps in the histogram on the left show where the 8-bit image information
was “stretched”—in other words, the 8-bit image is likely to suffer from posterization,
banding, or other nasty digital artifacts when you try to print it.
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