Vintage computers and video game systems, as well as other consumer devices, often offer more than one video output option. Composite and S-Video are two of the most common options. Let’s look at composite vs S-Video, and why one is better than the other.
S-Video separates the video signal into two components, the chrominance (color) and luminance (brightness), where composite transfers them both on a single wire. Separating the two gives a clearer picture, though the difference depends on how the circuit is implemented.
Where S-Video came from
S-Video gets its name from SVHS, a high-end VCR standard dating to the late 1980s. Arguably, VHS couldn’t really take advantage of the higher quality video signal, but SVHS could. But a nascent form of S-Video appeared much earlier, in 1979, with the Atari 800. The mini DIN connector we associate with S-Video dates to the late 80s, but Atari’s implementation was very similar to modern S-Video, and mostly compatible with it.
Other computer makers, notably Commodore, followed suit. Many off-the-shelf video chips generated the chroma and luma signals separately anyway, so implementing separated composite, as it was known then, was really simple. All you had to do was not mix the signals.
Many game systems from the 1990s and early 2000s support s-video.
Advantages of composite video
Composite video has one slight advantage, and that’s one reason certain computers never offered S-Video. If you alternate two colors closely together, they bleed and create a third color. We call this artifact color. Both the TRS-80 Color Computer and the Apple II took advantage of this. Some people went ahead and modded their Color Computers to get an S-Video output anyway, to get a clearer picture, but some software will lose those extra colors. The Atari 800 also had artifact color, which shouldn’t surprise anyone familiar with Jay Miner’s work.
If a certain software title doesn’t look right over S-Video, it’s because the artist who drew the graphics was using artifact color, and factored that bleeding into the design. The Wizard and the Princess on the Atari 800 and Canyon Climber on the TRS-80 Color Computer are two examples.
Advantages of S-Video vs composite
Generally speaking, the less mixing that you do of signals, the better your picture is going to be. RGB standards like VGA take this a step further, transmitting all three primary colors on separate wires.
S-Video is a step in that direction. It’s an intermediate step, but it provided an improvement while being cheap to implement. The result is a sharper picture and much clearer text. On some systems, the text output is fuzzy and uneven over composite, but looks just fine over s-video.Text will generally be clearer, more even, and easier to read over s-video. Graphics will be sharper too, and will generally look better, though they can also reveal the limitations of the low resolution these systems had.
On some systems the difference is more pronounced than others. It depends on the circuitry they used. Some s-video designs allow some leakage between the two signals, and the more leakage you get, the less dramatic the improvement.But if you have a choice, you’re almost always better off going with s-video instead of composite, if you can. Either will give an improvement over RF by eliminating interference, and the sharper picture from S-Video almost always looks better.