Sony DCR-DVD100 - Manual (Page 9)

D V D H a n d y c a m T E C H N O L O G Y H A N D B O O K
D
VD MEDIA
TECHNOLOGY
9
DVD Capacity
DVD-ROM, DVD-R and DVD-RW discs 12cm (4-3/4") in
size, which all share the same “one layer, one side”
structure, have a storage capacity of 4.7 GB --
approximately 7 times larger than the capacity of a CD
disc the same size. DVD Handycam camcorders use
smaller DVD-R or DVD-RW discs 8mm (3-1/8") in size.
4.7
GB
1.4
GB
● Comparison of CD-ROM and DVD-ROM
CD-ROM DVD-ROM
the minimum
pitch size
0.83µm
diameter of spot
1.4µm
Track pitch
1.6µm
the minimum
pitch size
0.4µm
diameter of spot
0.9µm
Track pitch
0.74µm
About Lasers and Lenses
DVD recording uses a short-wavelength red semiconductor laser. The wavelength of this laser is 650nm (nanometers). The
NA (numerical aperture) of the object lens used for optical pickup is 0.6. This combination yields a small-diameter “spotlight”
and high-density recording capacity. By comparison, CD recording uses a semiconductor laser with a wavelength of 780nm
and a NA of 0.45.
12cm (4-3/4")-diameter disc 8cm (3-1/8")-diameter disc
These smaller discs, single-sided with one recordable
layer per side, have storage capacity of 1.4 GB. Small
double-sided discs with one recordable layer per side are
also available for DVD Handycam camcorder recording;
these discs have a storage capacity of 2.8 GB -- enough
to hold approximately two hours of video recording.