In light of the magnitude of all of the talk about digital this and hi def that, there are a lot of us wondering what the differences are between the HD DVD format and Blu ray. Here in a nutshell is the scoop that will define the technical differences between these two. As a side note, in the Format War that ensued until 2008 between the formats, Sony with the Blu ray won when Toshiba announced that it would no longer be making HD DVD players after Warner Bros. switched to the Blu Ray format.



Both Blu Ray and HD DVD have the same wavelength that they use of 405nm, and both use a blue violet laser, but the optics are different. The Blu Ray discs have a tighter track pitch than the digital discs, so they hold much more information even with the laser being the same wavelength. With a tighter track pitch, it means that the BD has a single thread of data that spirals from the inside of the disc outward that is more compact than a pitch that is less tight, so more thread fits on it.

A lot of people have wondered why, when they use the same type of lasers, the two formats incompatible with opposite players. A Blu ray disc (BD) cannot play on a HD digital disc (DVD) player because of the track pitch that was previously discussed. Digital discs also have a different surface layer than BD. HD DVD uses a 0.6mm surface layer, which is the same as a regular digital disc, but BD has a much smaller layer (0.1mm), so the laser focuses at that aperture.

Blu Ray discs also have a special hard coating, called Durabis, that is applied to make sure that they are resilient to protect the data that is only 0.1mm below its surface. There is an extra benefit to having the layer of data that close to the surface, and that is that there is more room for extra layers and more data that can be put on them then on a HD DVD. The price of BDs is more expensive than their HD counterparts because new equipment is used to make them; the machines that make DVDs cannot make BDs because of the different coating, the data layer, and the track pitches. The bottom line here that is all about the technical differences between these two types of formats is that the Blu ray discs are more expensive, but they also hold more data.