by J.R. Powell

Created on: December 28, 2008

Blu-ray is a next generation optical disc format. Blu-ray discs are the same diameter as both CD and DVD discs, but the pits on a Blu-ray disc are a lot smaller than those on CD and DVD discs. This allows Blu-ray to hold a lot more data than those formats.

Blu-ray gets its name from the blue-violet laser which is required to read the smaller pits on Blu-ray discs. DVD discs can be read by a red laser, which is less precise than a blue-violet laser. Blu-ray players, as well as being designed to play back Blu-ray discs, can also play back standard definition DVD discs (subject to region code restrictions).

Blu-ray discs can hold 25GB (Gigabytes) on a single layer disc, and 50GB on a dual layer disc. Higher capacity discs have been produced in the lab, but these are the only types currently in use for pre-recorded media.

The Blu-ray format is primarily designed for the storage of films and TV content in high definition (1920x1080 pixels). To take full advantage of this resolution, you will need a 'full HD' (1920x1080 pixel) HDTV, though you can still watch Blu-ray content on lower resolution HDTVs, such as those with a resolution of 1280x768, and still see a big improvement over standard definition. The pixel resolution of high definition content on Blu-ray discs is 5 times the resolution of PAL standard definition DVDs (which have a resolution of 720x576 pixels), and 6 times the resolution of an NTSC DVD (which have a resolution of 720x480 pixels). Though the quality of the discs greatly depends on the films themselves and how they have been transferred to Blu-ray.

24fps

As well as the higher definition picture than DVD, Blu-ray discs allow content to be stored at 24 frames per second. This is the frame rate used in nearly all feature films. Though you will also need a compatible player and TV. Most players are compatible, and the newest HDTVs are also compatible with this frame rate. If you have a player or HDTV which is not compatible with this frame rate, you can still watch Blu-ray discs which have been encoded at 24fps, but you would need to set your player to output at 60i/p. The disadvantage is that if your TV is only compatible with 60i/p but not 24p, there will be slight added judder (sometimes called 3:2 pull-down judder) when playing back films. Though this judder is also in all NTSC film DVDs but not PAL film DVDs (but PAL DVDs have the disadvantage of being sped up to 25fps or 50i).

50/60Hz Content

As with standard definition, Blu-ray also allows content

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