channel in their raw data; as 16 bits is the smallest addressable unit larger than that, using it would allow the raw data to be manipulated. Expansions High dynamic range and wide gamut Some systems started using those bits for numbers outside the 0–1 range rather than for increasing the resolution. Numbers greater than 1 were for colors brighter than the display could show, as in high-dynamic-range imaging (HDRI). Negative numbers can increase the gamut to cover all possible colors, and for storing the results of filtering operations with negative filter coefficients. The Pixar Image Computer used 12 bits to store numbers in the range [-1.5,2.5), with 2 bits for the integer portion and 10 for the fraction. The Cineon imaging system used 10-bit professional video displays with the video hardware adjusted so that a value of 95 was black and 685 was white. The amplified signal tended to reduce the lifetime of the CRT. Linear color space and floating point More bits also encouraged the storage of light as linear values, where the number directly corresponds to the amount of light emitted. Linear levels makes calculation of light (in the context of computer graphics) much easier. However, linear color results in disproportionately more samples near white and fewer near black, so the quality of 16-bit linear is about equal to 12-bit sRGB. Floating point numbers can represent linear light levels spacing the samples semi-logarithmically. Floating point representations also allow for drastically larger dynamic ranges as well as negative values. Most systems first supported 32-bit per channel single-precision, which far exceeded the accuracy required for most applications. In 1999, Industrial Light & Magic released the open standard image file format OpenEXR which supported 16-bit-per-channel half-precision floating-point numbers. At values near 1.0, half precision floating point values have only the precision of an 11-bit integer value, leading some graphics professionals to reject half-precision in situations where the extended dynamic range is not needed. More than three primaries Virtually all television displays and computer displays form images by varying the strength of just three primary colors: red, green, and blue. For example, bright yellow is formed by roughly equal red and green contributions, with no blue contribution. For storing and manipulating images, alternative ways of expanding the traditional triangle exist: One can convert image coding to use fictitious primaries, that are not physically possible but that have the effect of extending the