The medium - the blank onto which the recorder writes - is one key to successful CD-R. Unfortunately, there is not the consistency one would wish among the various types. Several different forms are available at this writing (March 1999), distinguishable by the color of the active surface - the one that goes down and onto which the laser writes. They are gold, green and blue. None of them is 'best', and the gold and green vary greatly among brands. Even a single brand may have different product, depending on the actual manufacturer. There are also two different colors of metallizing layer: silver and gold. (The silver may either be silver or platinum.) The active color which seems to be green is actually blue, but made to look green by reflection from the gold metallizing.
It is the combination of medium and recorder that determines how well your discs come out. If someone finds that Brand X makes great audio discs, you may find them terrible because your recorder does not use them as well. Thus, you may want either to stay with the hardware manufacturer's recommendation or with the results reported on the newsgroups or the mail list. Note, too, that an audio disc that plays well in some CD machines may not be acceptable in others and that what works best for data may not handle audio as well.
Most media on the general market are of essentially the same length. There are slight variations, but whether the package is marked 650 MB, 680 MB or something else, it is almost certainly about the same size as any other with similar markings, as attested by the claim of 74 minutes. The longer discs (80 minutes), shorter ones (63 minutes) and shortest ones (smaller diameter, about 15 minutes) have been hard to find and often disproportionately expensive; the 80-minute discs were at one time harder to write successfully. Otherwise, the apparent difference in capacity is largely a marketing difference in counting megabytes and is of no practical interest. There is slight variation in actual length - a matter of a few seconds - but that is seldom important and may not be consistent even within a brand. There is a page on this in the Files section of this site with some measured lengths and a link to another such table.
E-mail me at cdrecording@mrichter.com
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