How does Photo CD work?

In a nut shell, 35mm film (negative, slide, B&W, internegative) is scanned by an image scanner and transfered to XA-formatted CD-ROM discs. These discs are manufactured by burning (writing) -- not by pressing.

Each scanned image on the disc is kept in five resolutions. These five resolutions are called: Base/16, Base/4, Base, 4Base, and 16Base. As examples, Base/16 is one sixteenth the resolution of the "Base" image, and 16Base is sixteen times the resolution of "Base". (These are not simply larger picture elements. There are in increased number of scan lines.)

The 4Base and 16Base images are are compressed using Huffman encoding. You need the decompression software to pull the higher resolutions out of the image. You would typically need these higher resolutions if you want enlargements or if you intend to use an HDTV as a display device.



Copyright ©1995 by ISOMEDIA, Inc.
For Information, contact Ken Cheney