Photo CD

Definition: Proprietary system of digital image management based on storage of image files (called Image Pacs) onto CDs. * The system scans an image to digitise it into Kodak's YCC format which is stored on the CD at five different levels of resolution; maximum capacity of disk is about 100 images. * The CD can be played back on any CD-ROM player in an Apple Mac-compatible or IBM PC-compatible computer that is multi-session compatible. Some Photo CD answers to questions you never asked Introduced in September 1990, the tricky and clever part of Photo CD is the Image Pac -- the files making up one image. After scanning, the digital file is written on the CD at five different resolutions: (1) Base/16: 128x192 pixels for thumbnails; (2) Base/4: 256x 384 pixels for low-res images; (3) Base: 512x768 pixels for TV quality; (4) 4 Base: 1024x1536 pixels for HDTV quality and (5) 16 Base: 2048x3072 pixels: the top resolution for Photo CD. The top res is 64 Base i.e. 2048x 3072 to 5230 pixels -- depending on format -- on Pro Photo CD. These files do not take as much room as you'd expect as they are not only compressed, they are stored as 'residues' i.e. higher resolutions are stored as differences from the lower resolution.

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