Each CCD records color information and outputs one 24-bit color value. This value makes up an individual pixel in the digital image. The higher the resolution of the scan, the greater is the number of data points recorded, and the larger the file size. Variations in dynamic range impact the quality of the scan more than simple resolution does. A scanner with a lower dynamic range records the two similar colors as the same value.
Illumination can also affect the quality of the scan.
For instance, CCD arrays require a consistent light source to illuminate the image evenly. Variations in illumination across the original can produce unwanted artifacts in the digital image. The accuracy with which light is focused onto the scanning head is one of the primary distinguishing qualities between desktop scanners and the high-end devices used in prepress houses. To receive the most accurate reading from any point on the image, CCDs in the scanning head require a finely controlled optical aperture. The color information for one pixel in the original image is focused precisely onto one, and only one, CCD in a scanner with excellent optics.