Optical Media Print

Optical media are CDs, DVDs and BDs (BlueRay discs). All three discs have approximately the same size, but different amount of storage capacity. They are read by a laser beam, which is why they are called optical media. CD's and DVD are scanned with a red laser beam. BD's in contrast with a blue laser beam that is substantially thinner than the red. Therefore, the BlueRay disc tracks are grouped more closely than those of CD's and DVD's, hence more storage capacity. The physical appearance of the DISKS is similar, but the structure and specifications are different:

cd_dvd_bd

- CD (Compact Disc), 600 MB: approximately one hour of music in CD quality.
- DVD-5 (digital video disc) 4.7 GB (single layered): Movies for about one hour in standard quality.
- DVD-9 (digital video disc) 8.5 GB (double layered): Movies for about two hours in standard quality. (Most Hollywood-Movies are issued on DVD9).
- BD (Blue-ray Disc) 25 GB (single layered): several hours movies in High Definition (HD)-quality

CD's and DVD's can be played with traditional players. BlueRays need a special device. This however, is backward compatible.