NTSC and PAL are two types of color encoding systems that affect the visual quality of content viewed on analog televisions and, to a much smaller degree, content viewed on HDTVs. While NTSC delivers a frame rate of 30 frames per second (fps) at an aspect ratio of 720x480, PAL uses a frame rate of 25 fps and a 720x576 aspect ratio. The PAL system offers automated color correction compared to NTSC's manual color correction. The NTSC standard is popular in places like the U.S. and Japan, while PAL is more common in countries such as the UK, Australia, and Sweden.
There is a third standard, called SECAM (Sequential Couleur Avec Memoire or Sequential Color with Memory), that is used in Eastern Europe and France.
Countries that use NTSC vs. PAL
NTSC systems are mostly limited to North America, parts of South America, Japan, Taiwan, the Philippines, and South Korea. PAL systems are much more common around the world and can be found in Australia, most of Western Europe, China, some parts of Africa, India, and elsewhere. A third system, known as SECAM, is found in France, Russia, and parts of Africa.
Differences in Color Encoding in PAL and NTSC
The PAL standard manages color automatically, using phase alternation of the color signal that removes hue errors. Also, chrominance phase errors are eliminated in PAL systems. NTSC receivers have a manual tint control for color correction, so if colors are off-hue, the higher saturation of NTSC systems makes them more noticeable and an adjustment has to be made.
Another technical aspect is that the alternating color information — Hanover bars — can lead to grainy pictures if there are extreme phase errors. This can even happen in PAL systems, especially if decoder circuits are not properly aligned, or with early-generation decoders. However, extreme phase shifts of this nature are seen more often in ultra high frequency (UHF) signals (less robust than VHF), or in areas where terrain or infrastructure limit transmission paths and affect signal strengths.
A PAL decoder can be seen as a pair of NTSC decoders:
- PAL can be decoded with two NTSC decoders.
- By switching between the two NTSC decoders every other line it is possible to decode PAL without a phase delay line or two phase-locked loop (PLL) circuits.
- This works because one decoder receives a color sub carrier with negated phase in relation to the other decoder. It then negates the phase of that sub carrier when decoding. This leads to smaller phase errors being cancelled out. However a delay line PAL decoder gives superior performance. Some Japanese TVs originally used the dual NTSC method to avoid paying royalty to Telefunken.
- PAL and NTSC have slightly divergent colour spaces, but the color decoder differences here are ignored.
- PAL supports SMPTE 498.3 while NTSC is compliant with EBU Recommendation 14.
- The issue of frame rates and color sub carriers is ignored in this technical explanation. These technical details play no direct role (except as subsystems and physical parameters) to the decoding of the signal.
Picture Quality in NTSC vs. PAL
PAL lines go out at 50 fields per second (since Europe uses a 50 hertz power supply), i.e., 25 alternating lines. PAL televisions produce 25 frames per second that causes motion to be displayed faster. PAL may have fewer frames per second, but it also has more lines than NTSC. PAL television broadcasts have 625 lines of resolution, compared to NTSC's 525. More lines means more visual information, which equals better picture quality and resolution.
Conversion from NTSC to PAL and vice versa
If a PAL movie is converted to an NTSC tape, 5 extra frames must be added per second or the action might seem jerky. The opposite is true for an NTSC movie converted to PAL. Five frames must be removed per second or the action may seem unnaturally slow.
PAL and NTSC on HDTVs
There is still a broad analog system in place for television, so even though digital signals and high-definition (HD) are becoming the universal standard, variations remain. The primary visual difference between NTSC and PAL systems for high definition TVs (HDTVs) is in the refresh rate. NTSC refreshes the screen 30 times a second, while PAL systems do so 25 times a second. For some types of content, especially high-resolution images (such as those generated by 3D animation), HDTVs using a PAL system may show a slight "flicker" tendency. However, the image quality is equal to that of NTSC and most people won't notice any problem.