Kodak has made at least two significant contributions to digital imagery with Photo-CD. First, anyone can have a custom CD-ROM written for a low price ($20-$30) as easily as having a roll of film processed. In the past, writing anything on CD-ROM was an expensive, tortuous task. Second, images can be read directly from CD-ROM in five different sizes (resolutions): full: 2048x3072; 1024x1536: about the resolution of digital TV; 512x768--the base image: about the resolution of standard TV or a VGA monitor; 256x384: snapshot size; and 128x196: thumbnail size. All of these sizes feature 16 million different colors (24-bit color).
The ability to read these various sizes directly from the disc is important because one does not have to read the full image from the Photo-CD to view one of the smaller sizes. An image at full Photo-CD resolution requires about 6 megabytes of storage on the CD and 18MB when decompressed; it requires at least five minutes to read one full image into the computer. (This is a limitation of current CD-ROM technology.) However, only about ten seconds is required to read standard TV quality image. Therefore, one can conveniently view Photo-CD images at TV/VGA or lesser resolution with acceptable response time. High-resolution viewing or printing is available but at the price of a longer access time.
Kodak uses a gold foil in the Photo-CD. This should increase the archival quality of the discs. Images can be copied directly from a disc in Photo-CD format or converted to many other popular image formats such as .PCX, .BMP, .TIF, and .GIF
When the film is initially scanned using the Photo-CD System, each image uses a palette of 32 billion colors (36 bits). If the image is a negative, it is digitally converted to a positive. Also, it is possible at this time to apply color correction digitally for film type and/or exposure conditions if they are known. The palette is reduced to 16 million colors (24 bits) before it is written to CD-ROM. The image is also digitally compressed by about a factor of three with no loss in quality.
Currently, the only way to copy the images from a Photo-CD onto the server is one at a time via undergraduate student. This is a bottleneck in the process which adequate software will eventually remove. Also during the copying process, it is desirable to trim the extraneous margin material from the images. This makes them more attractive to view, reduces disk space, and decreases access time.