CD player in 1970. Following litigation, Sony and Philips licensed Russell's patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s. The Compact Disc is an evolution of LaserDisc technology, where a focused laser beam is used that enables the high information density required for high-quality digital audio signals. Prototypes were developed by Philips and Sony independently in the late 1970s. In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the "Red Book" CD-DA standard was published in 1980. After their
Photo CD their film negatives and transparencies. The Kodak Pro Photo CD Master Disc contains 25 images with maximum resolution of 6144 x 4096 pixels (six resolutions per file, Base/16 to 64 Base). This type is appropriate for 120 film, 4x5, but also for small picture film, if highest resolution is required. Separate from the Photo CD format is Kodak's proprietary "Portfolio CD" format, which combines Red Book CD audio and Beige Book PCD with interactive menus and hotspots on PCD images. Some standalone Philips Photo/Audio CD players could play Portfolio CDs, and Windows player application was freely available. The Kodak Portfolio