Composite artifact colors

"Artifacting" redirects here. For other uses of the term, see Artifact.

Composite artifact colors is a technique commonly used to address several graphic modes of some 1970s and 1980s home computers. With some machines, when connected to an NTSC TV or monitor over composite video outputs, the video signal encoding allowed for extra colors to be displayed, by manipulating the pixel position on screen, not being limited by each machine's hardware color palette.

This mode was used mainly for games, since it limits the display's effective horizontal resolution. It was most common on the IBM PC (with CGA graphics), TRS-80 Color Computer, Apple II and Atari 8-bit computers, and used by the Ultima role-playing video games. Software titles (such as King's Quest for the IBM PC) usually provided an option to select between "RGB mode" and "Color Composite mode".

On PAL displays the effect is also present, but generates more limited colors. Depending on the exact PAL system used results will vary (if PAL-M or PAL-N are used, color artifacts similar to NTSC might be possible).

Although related, artifact colors are not the same as horizontal blurring. Blurring is a general effect of using a composite connection, that simply creates new colors due to a mix of adjacent horizontal pixel values. The exact mix will depend on the saturation and specific colors of the original pixels. Nevertheless, this effect can be exploited by using dither patterns, generating new intermediate palette colors on machines with a sufficiently high resolution display, like the ZX Spectrum, Mega Drive/Genesis, NES/Famicom or Amiga.

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