The basic concept behind high-definition television is actually not to increase the definition per unit area ... but rather to increase the percentage of the visual field contained by the image.
The majority of proposed analog and digital HDTV systems are working toward approximately a 100% increase in the number of horizontal and vertical pixels. (Proposals are roughly 1 MB per frame with roughly 1000 lines by 1000 horizontal points). This typically results in a factor of 2-3 improvement in the angle of the vertical and horizontal fields. The majority of HDTV proposals also change the aspect ratio to 16/9 from 4/3 - making the image more "movie-like".
The following table summarizes a few of the more conventional analog HDTV proposals in comparison with existing TV systems.
Name Prog. Total Active Vert. Horz. Opt. Asp. Vert. Horz. freq.
or lines lines res. res. view ratio field field MHz
inter. dist.
HDTV p 1050 960 675 600 2.5H 16/9 23 deg 41 deg 8
USA,
analog
HDTV p 1250 1000 700 700 2.4 16/9 23 deg 41 deg 9
Europe,
analog
HDTV NHK i 1125 1080 540 600 3.3 16/9 17 deg 30 deg 20
NTSC i 525 484 242 330 7 4/3 8 deg 11 deg 4.2
conv.
NTSC p 525 484 340 330 5 4/3 12 deg 16 deg 4.2
prog.
PAL i 625 575 290 425 6 4/3 10 deg 13 deg 5.5
conv.
PAL prog p 625 575 400 425 4.3 4/3 13 deg 18 deg 5.5
SECAM i 625 575 290 465 6 4/3 10 deg 13 deg 6
conv.
SECAM p 625 575 400 465 4.3 4/3 13 deg 18 deg 6
prog
NOTE: The aspect ratio of the picture is defined to be the ratio of the picture width W to its height H. The optimal viewing distance (expressed in picture heights, H) is the distance at which the eye can just perceive the detail elements in the picture.