Blu-Rays cannot be played in a traditional DVD player, which means that you will eventually have to buy a blu-ray player. However, all blu-ray players can play DVDs, and they upscale the images to look better on an HD screen, up to 1080p. So, while you will have to get a new Blu-Ray player to play HD movies, you can still see all of your current DVDs on the same player, and they'll be enhanced. Blu-ray is essentially the next generation of DVD. A blu-ray disc looks like a regular DVD but must be played in a blu-ray player, not a regular DVD player. Blu-ray discs can hold much more data than regular DVDs, which makes them good for carrying movies in HD. If you don't have a HDTV yet, then don't worry about blu-ray. While you can use a blu-ray player with a regular TV, it won't look any better than your existing DVD player and DVDs. Even so, regular DVD is not going anywhere. Expect to see new releases on BOTH DVD and blu-ray for the foreseeable future. If you do decide to buy a blu-ray player, it will also play your existing DVDs - so you lose nothing by upgrading.
Lasers are used in both media to read the information stored on the disc. As the disc spins the laser reads the information and transfers both picture and sound to the television.
- DVD- DVD players use a red laser at 650nm wave length to read DVD discs. As the disc spins the laser reads the information encoded on the media and produces an image and sound on your television.
- Blu-ray- Like the name suggests Blu-ray players use a blue laser to read the stored information. Blue laser wavelengths are shorter than the red at 405nm and are about two and a half times smaller in diameter than red lasers. This allows for closer and more precise reading of information stored on the disc.
Physically, Blu-ray and DVD discs are identical. Both media have grooves or pits on their bottom layer than enables the laser to penetrate through and read the stored information.
- DVD- Since DVDs are read with a red laser the grooves on its underside need to be wide enough to accommodate the larger wavelength. Because the grooves are so far apart only 4.7 GB of information can be stored on each layer of the disc. DVDs also include a protective layer designed to resist scratching.
- Blu-ray- The grooves on a Blu-ray disc are much thinner and closer together because the blue laser used to read the disc has a shorter wave length and is two and a half times thinner than the red laser. This allows the Blu-ray disc to squeeze almost five times as many grooves on to a disc exactly the same size as a DVD. Blu-ray also includes a protective layer to prevent scratches. This protective layer is physically thinner than the one on a DVD, but it has a hard coating that makes it more scratch resistant.