What Should I Look For In Blank CD, DVD, and Blu-Ray Discs?

June 2, 2009

in digital media

by David Hakala

CD and DVD recording media are simple plastic things that should be easy to buy. But there is quite a bit to know about blank discs before you purchase.

First, there’s spelling. ‘Disk’ refers to magnetic media such as hard drives and floppies (if you remember floppies). “Disc” refers to optical media such as CD, DVD, and Blu-Ray.

Next, there are discs that can be recorded only once and discs that are “re-writable”, that can be erased and recorded again just like magnetic disks. A CD-R disc is record-once, a CD-RW is re-writable. A DVD-R or DVD+R is record-once, and a DVD-RW or DVD+RW is re-writable.

Data is recorded on an optical disc by melting tiny pits in a metal coating with a laser beam, so how can a disc be re-writable? Amazingly, the laser can re-melt the pits in a re-writable disc and the surface will smooth out again, like erasing pencil marks and re-using paper. Re-writable discs use a different sort of metal than record-once discs.

The difference between ‘DVD-“ and “DVD+” is negligible, just two slightly different competing standards. Most drives and players will use both, but check the specs of your device before you buy if it is a very old device.

DVD-RAM stands for “Random Access Memory.” This type of disc is required by some camcorders. DVD-RAM provides better error control and more re-writes (estimated at 5,000 to 10,000 rewrites), but that may not matter in computer use. DVD-RAM generally costs considerably more than other formats.

DVD-DL means “double layer.” You can fit 8.5 GB of data on a DVD-DL versus about 4.75 GB on single-layer DVDS. A CD can hold only 600 to 800 MB of data. Again, DVD-DL costs more.

It is tempting to buy generic discs to save money, but that’s often a mistake. Low-quality discs fail during writing and reading more often than brand names. You may well end up discarding all the money you saved and more. The metal coating on discs deteriorates over time, so the disc you recorded today may be unreadable when you need the data. Brand name discs generally last longer.

David Hakala has perpetrated technology tutorials since 1988 in addition to committing tech journalism, documentation, Web sites, marketing collateral, and profitable prose in general. His complete rap sheet can be seen at http://www.linkedin.com/in/dhakala


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