9. Blu-ray

A Blu-ray disk is an optical storage device similar to CD and DVD technology. It also uses a laser to read and write to the disk, but instead of a red laser beam, as used in DVD and CD, it uses a blue-violet laser beam.


This means it can burn smaller pits on the disk and so it has even more storage capacity than a DVD.

A single layer Blu-ray can store 25Gb whilst a double layer Blu-ray can hold up to 50Gb of data.

Blu-ray is commonly used to store high definition films (HD).

You can also purchase a blu-ray burner for home use as a backup device or to store home movies.

There are three format in the specification.

  • BD-ROM - read-only format for distributing HD films, computer games, software etc
  • BD--R one-time recordable format for HD video recording and data storage
  • BD-RE rewritable format

There are also plans to make a BD/DVD combination that has Blu-ray and DVD formats on the same disk so it can be played in both DVD and Blu-ray players.

A single layer disk (25GB) can hold about 4 hours of high definition video or about 12 hours of standard definition video. This huge capacity is very useful for storing training courses in video format.

Advantages of Blu-ray Disadvantages of Blu-ray
Very large storage capacity 25-50 Gb Blu-ray does not work in DVD or CD drives
Sound and picture quality is excellent, making them ideal for storing HD films. They can be easily damaged by breaking or scratching
Blu-ray disks are now mass produced so they are relatively cheap Using a Blu-ray for backup means that up to 50 GB of data is stored on disk, which may then break. That is a lot of data to lose. Perhaps splitting it into several DVD is less risky.
A hybrid Blu-ray / DVD disk can be read in both a Blu-ray and DVD player  
Properties of a Blu-ray
Property Notes
Type of storage Optical
Data access Direct access
Cost of storage Blu-ray cost more per byte of storage than hard disks or magnetic tapes.
Capacity 25 Gb (single layer) to 50Gb (double layer)
Speed Slower than a hard disk or flash memory, faster than magnetic tape

Fairly portable. Too large to fit into a pocket, but will easily fit inside a bag. Can be carried between home/school/office.


Easily scratched by general wear and tear or by not protecting it in a plastic case. Scratches on the disk surface can damage the data being stored

Needs to be protected from extremes of heat.

Has a limited number of read/write cycles.


If scratched, the data might not be able to be read.

Needs a computer with a Blu-ray drive in order to read the disk. Cannot be read by a CD drive or DVD drive.

Challenge see if you can find out one extra fact on this topic that we haven't already told you

Click on this link: Blu-ray recording equipment