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The Blu-ray disk (BD) is a high-capacity optical storage system. Blu-ray uses a laser to read or write data from or to a spinning reflective disc in a manner similar to that used by traditional DVD or CD players and recorders. However, the quantity of information that can be stored on a standard-size disk is limited by the wavelength of the laser used to burn or read the disk. Standard DVD technology uses red laser technology operating at a wavelength of 650nm. The laser used in a Blu-ray disk drive is blue-violet and operates at a shorter wavelength of 405nm.This means that the laser can be focused with greater precision, and consequently on narrower tracks. Substantially more data can therefore be stored on a Blu-ray disk. Standard disks are the same physical size as traditional DVDs, although a smaller 8cm version, known as Mini-Blu-ray, is also available - primarily for use in digital camcorders. 

A rewritable Blu-ray disk with a data transfer rate of 36Mbps (basic 1x speed) has a potential capacity of 25GB of data on a single-layer disc and 50GB on a dual-layer disk. On a 50GB disk, this translates into 9 hours of high-definition (HD) video or approximately 23 hours of standard-definition (SD) video. The Blu-ray format was developed jointly by Hitachi, LG Electronics, Matsushita, Mistubishi, Pioneer, Philips, Samsung, Sharp, Sony and Thomson.

For digital photographers, Blu-ray probably represents an important next phase in the fast-changing world of storage technology. With at least five times the capacity of traditional DVDs, its advantage is obvious. However it is not directly compatible with existing DVD technology and as computers are increasingly supplied with Blu-ray drives, the future of all those traditional DVDs packed with archived images looks increasingly uncertain. Some manufacturers have produced drives capable of reading both traditional and Blu-ray DVD technology, but currently they seem to have made little impact on the market.

Some companies are producing four and sixteen-layer Blu-ray disks with potential capacities of 100Gb or 400Gb respectively. Rewriteable versions are also under development. A 1TB Blu-ray disk is forecast by 2013.


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