Fundamental properties of digital images.
The quality of a digital image is affected by matrix size, unsharpness in the underlying image, bit depth, and noise in the underlying image. The array of all of the pixels into which an image is divided is the image matrix. If the image matrix is small (ie, composed of a few large pixels), the resolution of the digital image is low. Image blur dominates when the pixel size is much smaller than the unsharpness of the underlying image. The density in a pixel is represented by a binary number with a variable number of bits (bit depth). The more noise present in the initial image, the fewer the bits that are needed to convey its representation. Insufficient numbers of bits in the digital representation of an image, whether from too few pixels or too small a bit depth in each pixel, result in inadequate image quality. Use of too many bits, relative to the quality of the underlying image, places an increasingly unwarranted demand on digital image handling and processing.
Balter
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Philips Medical Systems North America, Shelton, CT 06484.
D000703:Analog-Digital Conversion; D011856:Radiographic Image Enhancement