The latest issue (14/2005) of the German computer magazine c't has a comprehensive test of DVD media (44 types). I'm working on a summary which will go up later today (I'm at home with back problems
One of the interesting things they found, though, is that the 16x DVD dash
-media generally performs better than the plus
-media. And they tried to find out why this is.
One of the properties they examined in determining the physical quality index is the radial tracking error (RadialN) which describes the departure of the embossed groove from the ideal position. The DVD+ norm specifies max. 25 nm for 3000 rpm, the measured values were all 3-8x higher
- up to 200nm! Strangely, the DVD- values were generally lower (ca. 40-70 nm).
c't suggests that this high value may result from the higher wobble frequency
of the groove, which helps laser tracking: this is 817 kHz for plus-media as opposed to 140.6 kHz for dash-media. This allows a simpler manufacturing process (no land prepits) but seems to have drawbacks for high-speed burns and may be the reason for the high radialN values!
I find this intriguing and would appreciate hearing from people with more experience with 16x media or technical expertise!
Ian? dolphie? RJW?
The summary is up in the c't burner test thread