Plextor PX-712UF Installation And User Manual page 66

Section 4. Advanced Features and PlexTools Professional
What the Measurements Mean
Recordable and rewritable discs can be manufactured with widely
varying quality, and a failure to write a disc without errors can be caused
by either the drive or by the media. Variations in the reflective layer,
polycarbonate thickness, eccentricity (that is, if the spindle hole is not in
the exact center of the disc), and the quality and thickness of the dye
layer are all factors that determine if the laser accurately burns the data
on to the disc.
PoweRec can reduce the drive speed during recording to ensure a higher
quality recording, but the reduction in speed may be perceived as a
problem with the drive when compared against a drive without
PoweRec.
The FE/TE graphing capability of the Plextor PX-712UF drive displays
the mechanical characteristics of the disc by indicating how consistently
the laser tracks across the surface of the disc, and how accurately the
focus is maintained on the recording dye layer.
To be specific:
• Focus error is a measure of how accurately the laser is focused on
the disc surface. (That is, how round the laser dot is.) A good disc
will show a low number of focus errors across the graph. A bad disc
will show a high number of focus errors across the graph, or high
points where the drive cannot focus the laser correctly because of
poor disc quality.
• Tracking error is a measure of how accurately the laser tracks in the
disc's pre-groove area of the disc—that is, how well the laser
follows the spiral. A good disc will show low tracking error across
the graph, showing a fairly consistent track at all rotational speeds. A
bad disc will show high tracking error, which is caused by
eccentricity or poor quality of the manufactured media.
The FE/TE test result shows maximum writing speed for each media.
However this maximum writing speed is specific for a particular drive;
you cannot assume this speed applies to any other drive. If your discs
consistently show high rates of focus error or tracking error, you should
probably try a disc from a different vendor.
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PX-712UF Installation and Users Manual