You’ve probably heard these words, often accompanied with “and DVD” on any commercial for the latest movie release. But what exactly is blu ray, and how is different than DVD? They’re both disks, right? You probably know that blu ray is better format than DVD – maybe you even know that blu ray can play high definition video, while DVD can only play standard definition. But what does that mean? And why is that true? The clue is in the name – blue ray. To see why video is better with blue, we first have to understand how the data is stored on a DVD.
A standard DVD is a series of concentric grooves. If you hold a DVD up to the light, you can probably see the grooves as they reflect and refract light. If you zoomed in on these grooves, you’ll see that they’re really a series of tiny “pits”, physical indentations that are about as long as a bacterial cell is wide1. By shining a red laser at these pits and detecting the reflected light, a DVD player is able to read the information written by the series of pits. The smaller the size of the pit, the more information a disk can hold1. However, the pit size and distance between pits is limited by the type of light used to read the disk. Light is a wave, and the size of the pit has to be comparable to the wavelength of the light.
Instead of using red light, blu-ray uses – you guessed it – blue light. Blue light has a much shorter wavelength than red light, allowing for smaller pits and less distance between the pits2. As a result, the amount of information a blu-ray disk can store is much more than the amount a DVD can store. Thus, though a DVD can store a standard movie, it doesn’t have enough space to store a high definition movie2. HD movies have much more detail in each shot – the details are more defined. As a result, they take up close to five times as much space as a standard definition movie, greatly exceeding the capacity of a DVD. However, blu-ray discs have just enough space to store these HD movies2. The downside is that normal DVD players can’t play blu-ray discs – you need to buy a special blu-ray player for that.
The amount of information a blu-ray disk can store is much more than the amount a DVD can store
While blu-ray discs offer much better quality video, they have become much less popular in recent years, mostly due to the popularity of online streaming services3. While blu-ray was poised to be the next big thing in video recording, only time will tell if you’ll keep being told to “own it on Blu-Ray” in the future.