They use drum scanners, which offer vastly superior resolution and dynamic range when compared with flatbed scanners. They offer resolutions starting at 8,000 pixels per inch and going up to about 14,000 pixels per inch. However, resolution IS NOT a good indication of scanner quality. Color transparencies have a dynamic range of about 4.0.
Dynamic range is measured on a logarithmic scale.
A dynamic range of 4.0 is much, much higher than 3.7, which is itself much, much higher than 3.2. Typical flatbed scanners have a dynamic range of 2.4. Resolution is less important, because an image rarely needs to be over 400 pixels per inch at the reproduction size for offset printing. It means the scanner cannot pick up detail in the shadows. Scans made on a scanner with a low dynamic range are flat, muddy, and dark, lacking in contrast and shadow detail, when compared with the same scan made on a scanner with a better dynamic range.