First announced back in 1990 but not available until 1992, Photo CD is a standard for CD-R discs and drives to store photos. The current version 1.0 of the Photo CD standard was published in December 1994.

You simply drop off a roll of film at a participating Kodak developer, and they digitize and store the photos on a specially formatted CD-R disc called a Photo CD, which you can then read on virtually any CD-ROM drive connected to a PC running the appropriate software.

Originally, Kodak sold Photo CD "players"designed to display the photos to a connected TV, but these have since been dropped in favor of simply using a PC with software to decode and display the photos.

Perhaps the main benefit Photo CD has brought to the table is that it was the first CD format to use the Orange Book Part II (CD-R) specification with multisession recordings. Additionally, the data is recorded in CD-ROM XA Mode 2, Form 2 sectors so more photo information could be stored on the disc.

Using the Photo CD software, you can view your photographs at any one of several resolutions and manipulate them using standard graphics software packages. When you drop off your roll of film, the Kodak developers produce prints as they normally do. After prints are made, they scan the prints with ultra-high-resolution scanners.

To give you an idea of the amount of information each scan carries, one color photograph can take 15MB–20MB of storage. The compressed, stored images are then encoded onto special writable CDs, and the finished product is packaged and shipped back to your local developer for pickup. Some developers can do the scanning on-site.

Photo CD Disc Types

The images on the disc are compressed and stored using Kodak's own PhotoYCC encoding format, which includes up to six resolutions for each image, as shown in Table 1.

Base	Resolution (Pixels)	Description
/16	128x192	Thumbnail
/4	256x384	Thumbnail
x1	512x768	TV resolution
x4	1,024x1,536	HDTV resolution
x16	2,048x3,072	Print size
x64	4,096x6,144	Pro Photo CD master only

Kodak has defined several types of Photo CDs to accommodate the needs of various types of users. The Photo CD Master disc is the standard consumer format and contains up to 100 photos in all the resolutions shown in the table except for base x64.

The various resolutions supply you with images appropriate for various applications. If, for example, you wanted to include a Photo CD image on a Web page, you would choose a low-resolution image. A professional photographer shooting photos for a print ad would want to use the highest resolution possible.

The Pro Photo CD Master disc is intended for professional photographers using larger film formats, such as 70mm, 120mm, or 4''x5''. This type of disc adds an even higher-resolution image (4,096x6,144 pixels) to those already furnished on the Photo CD Master disc. Because of this added high-resolution image, this type of disc can hold anywhere from 25 to 100 images, depending on the film format.

The Photo CD Portfolio disc is designed for interactive presentations that include sound and other multimedia content. The high-resolution images that take up the most space are not necessary here, so this type of disc can contain up to 700 images, depending on how much other content is included.

Multisession Photo CDs

One breakthrough of the Photo CD concept is that each of the disc types is capable of containing multiple sessions. Because the average consumer wouldn't usually have enough film processed to fill an entire disc, you can bring back your partially filled CDs each time you have more film to develop. A new session can then be added to your existing CD until the entire disc is filled. You pay less for the processing because a new CD is not necessary, and all your images are stored on a smaller number of discs.

Any XA-compliant or XA-ready CD-ROM drive can read the multiple sessions on a Photo CD disc, and even if your drive is not multisession capable, it can still read the first session on the disc. If this is the case, you must purchase a new disc for each batch of film you process, but you can still take advantage of Photo CD technology.

Kodak provides software that enables you to view the Photo CD images on your PC and licenses a Photo CD import filter to the manufacturers of many desktop publishing, image-editing, and paint programs. Therefore, you can modify your Photo CD images using a program such as Adobe Photoshop and integrate them into documents for printing or electronic publication with a page layout program such as Adobe PageMaker.

Picture CD

Although Kodak still offers Photo CD services, the high cost has led to limited popularity. Kodak now offers the simpler Picture CD service. Unlike Photo CD, Picture CD uses the industry-standard JPEG file format. It uses a CD-R, with up to 40 images stored at a single medium-resolution scan of 1,024x1,536 pixels.

This resolution is adequate for 4''x6'' and 5''x7'' prints. The images can also be made available via Kodak PhotoNet, where the same images are posted online and can be downloaded. In addition, Kodak has a service called Picture Disk that stores up to 28 images on a 1.44MB floppy disk at a resolution of 400x600, suitable for screensavers and slide shows.

The software provided with Picture CD enables the user to manipulate images with various automatic or semiautomatic operations, but unlike Photo CD, the standard JPEG (JPG) file format used for storage enables any popular image-editing program to work with the images without conversion.

Although the image quality of Picture CD isn't as high as with Photo CD, the much lower price of the service should make it far more popular with amateur photographers. Services similar to Picture CD are also offered by Fujifilm and Agfa, and some stores allow you to order Kodak Picture CD with your choice of store-brand or Kodak film processing.