How can we look the same, but be so different?

Today's post is brought to you by YesVideo's marketing team. Eber Legarreta digs into the differences between two media formats that look the same at first glance.

 Side by side, DVD and Blu-ray discs look identical. The main visible difference is the color on the bottom recordable surface of each disc. A DVD is bluish purple, and a Blu-ray is dark gray. While they may look the very similar, these two disc formats are unique in their capacity and function.

Disc Capacity
Capacity is one of the main differences between the two disc formats.

Single layer DVD: 4.7 GB
Single layer Blu-ray: 25 GB

Both discs are 8 cm in diameter, but a Blu-ray disc can hold five times as much information as a DVD. This is due to two key characteristics of each format –the compression of the information stored in each disc, and the laser that reads each format.

Data Compression – packing it all in!
A Blu-ray disc stores data in a far more compressed space than a DVD disc. Ever packed luggage for a long vacation? Pile all your clothes in one suitcase, and the zipper barely closes – that’s a DVD. Fold, organize and compress the same pile of clothes in the same suitcase. You

have room left over, and the zipper closes just fine – that’s a Blu-ray disc. This compression (at a microscopic scale!) is what allows a Blu-ray disc to hold so much more data than a DVD.

The Lasers – Red vs Blue
Due to the compression of data in Blu-ray, the laser required to read these discs also needs to be more concentrated. The red lasers used to read DVDs can’t read Blu-ray discs because they are not concentrated enough to process the tiny data particles of a Blu-ray disc. This is similar to trying to read very small text without a magnifying glass.

blue lasers used to read Blu-ray discs are focused to read the compressed data, as well as the data on a DVD disc. This is why most Blu-ray players are able to play both DVD and Blu-ray discs, but DVD players are limited to only playing DVDs.

Figure 1 DVD and Blu-ray laser comparison. http://www.blu-raydisc.com/en/AboutBlu-ray/WhatisBlu-rayDisc/BDvs.DVD.aspx

So…Blu-ray is the best format, right?
Overall, Blu-ray is a major upgrade over DVDs and there are many technical details to support this.

From a video standpoint, they allowsthe storage and playback of large, rich, high-definition video – which looks amazing on an HD display. However, not all video is recorded in high definition.

For all the standard definition video out there (which is the majority of personal video recorded before 2008), DVD is a perfect media format. SD video doesn’t require the capacity and HD-playback capabilities of a Blu-ray disc. And while Blu-ray and HD televisions have recently become more affordable, not everyone has the equipment to play Blu-ray discs.

So hold on to your DVD players. Whether they are on your living room or your computer, DVDs have not gone away just yet.

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