Right... technical stuff so get the coffee out.
Picture is made from Luminance
and Chrominance (C), Chrominace is made of the colour difference signals (U and V), the being the subtraction of the Red and Blue signals from the luminace. Green is worked out from these signals.
NTSC is 525 lines (about 483 visable lines) at 59.94 (the weird frame rate is to do with the colour carrier) frames a second. However the screen is interlaced (draws every other line then the next frame draws in the lines it missed and repeats) so you only get 29.97 frames. Horizontal scan rate is 15.73425Khz (59.94x525/2)
PAL is 625 lines (about 576 visable lines) at 50 frames a second (25 frames interlaced). Horizontal scan rate is 15.625Khz (50x625/2). Notice the similar HSR, this is intentional as it means that tubes designed for NTSC will work for PAL. If PAL was 60Hz and 625 lines it would require a much higher scan rate and the monitors wouldn't be compatable...
So the differences?
The gaps between the lines in NTSC is more visable so the picture looks darker...
NTSC also uses a low frequency colour carrier (3.58Mhz) which means that noise from the Luminance signal is likely to creep in.
NTSC also has poor colour hues due to the low frequency colour carrier and slight phase shifts of the U and V signals. This is why NTSC TVs (and if you look at the on screen menu a new option will appear...) have a tint control so you can adjust the green level.
PAL alternates the Phase in each frame so that phase shifts don't happen as much so green is er green.
Some NTSC curcuits will have a Hue compensator circuit which tries to make reds and pinks better however some other colours go slightly off (cyans and magentas...)
NTSC has a lower Gamma then PAL, so it does appear slightly darker.
PAL flickers due to the 4.97 Frame difference
PAL 60 is 525 Lines at 60Hz (horizontal scanning frequency 15.625KHz), it's not 625 lines (or 576 lines) as this would require the horizontal scanning frequency to be higher (18.73125Khz...). PAL 60 is technically PAL 59.94... but that doesn't trip off the tongue.
NTSC is inferior to PAL in terms of resolution and hue handling, but better circuit design has meant that the difference aren't as bad as they were in the 70s and 80s. Although whack up a test card on both and you'll soon see the differences...
Klik om te vergroten...