Difference between Blu ray and DVD

Difference between blu ray and DVD

Like many people, you might have heard of blue ray film and thought that that’s the movie’s title.

That’s far from the truth and the reality is that blu ray discs are a better version of the ordinary DVD.

In fact, they look the same in size and shape and the difference is in the functionality aspects such as resolution, storage capacity, player compatibility, laser reading technology and so on.

Let’s see these differences

(i)                 Storage capacity

A single layer DVD stores up to 4.7GB data and a double DVD can hold up to 8.7GB of data. This amounts to about 2 and 4 hours of standard definition movies respectively.

By comparison, a single layer Blu-ray disc can store almost 25 GB data, which is equivalent to 2 hours of HD movie and 13 hours of SD film. A double layer blue ray disc stores up to 50GB data, equivalent to approximately 4 ½ hours of HD information and 26 hours of standard definition information.

With the best portable bluray player, you can watch standard movies for a day non-stop.

(ii)               Disc design

Both discs have identical shapes with grooves on the underside for laser penetration. However, the differences in laser technology lead to differences in groove construction.

DVDs use a larger wavelength red laser to read information thus the underside grooves are wider to accommodate this wavelength. The need for wider grooves leads to lesser information (4.7 GB) stored per layer of DVD.

Blue-ray discs use a blue laser to read information. Blue wavelength is about 2 ½ thinner than a red wavelength and thus the blu-ray grooves are much thinner. More grooves can thus be squeezed in a single layer, accommodating more information than a DVD. The thinner grooves are more delicate and thus the protective layer on the underside has a higher scratch resistance than bluray.

(iii)             Laser reader

The decoder in a DVD player is a red laser of 650nm wavelength. The laser reads the encoded information as the disc spins to produce images and sounds on screen.

A bluray player on the other hand uses a blue laser of 405nm wavelength with less than half the diameter of red laser. The reading of data is thus closer and more precise.

Image resolution

DVDs use the standard definition resolution of 480p with a few having the enhanced definition of 520p. The blu-ray disc on the other hand stores between 1080p high definition and 2160p UHD resolution which are currently the clearest on a HD TV.

The question about what is the difference between Blu-ray and DVD? is a very pertinent question among member of the public and we hope this explanation as well as the linked site will help to make things clear.