Spotlight Article: Single vs. Dual Layer DVDs
Generally, a standard single-layer recordable DVD will hold about 4.7GB of information, which is a lot less than most movie DVDs hold because those already use the dual-layer technology. And you would think dual-layer would hold twice the information, or about 9.4GB of data. But, the truth is you lose about 10% capacity because of how the data is written to the second, or upper layer of the disc, leaving less usable space.
The consumer dual-layer discs you buy at the store are semitransparent, and burners and players make a very small adjustment in the focus of the laser's lens to read the upper layer of the DVD through the bottom layer.
In contrast, pressed movie DVDs use a reflective layer stamped with physical bumps that represent the digital "1"s and "0"s that make up a movie, whereas burnable DVDs use an organic dye that changes its opacity when exposed to heat - mimicking the bumps of pressed DVDs.
Hollywood has been pressing movies on dual-layer DVDs for a while now, which makes it hard if you are going to be "archiving" those store-bought movies for your own personal reasons...not that we approve of that or anything. Thus, buying a dual-layer burner makes the most sense.
I've found that dual-layer discs I've burned usually work in my standard DVD player, but there really is no guarantee. The best comparison is when CD burning was the fad. Older CD players were less likely to read homemade discs, while newer ones have little problem.
The one down side to single vs. dual-layer recordable DVDs today in the disc price itself. Because demand for the dual-layer is still relatively low at this point, the single layer sell for a lot less money. Like everything else, the price will become more reasonable in the future as more people buy the more expensive dual-layer discs. Demand increases, production increases and prices fall. Welcome to a free market economy.
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