color wheel
On 12/12/2012 12:47 PM, Thomas Richter wrote:
On 12.12.2012 09:15, Dale wrote:
My Uncle is an artist
I have ten years work experience as an imaging system engineer
I was always under the impression that CMY were the color complements or
opposites of RGB
he and apparently many others use a color wheel where the are other
complements or opposites to RGB
does anyone know why this situation is? are there two rights or is
someone wrong?
All wrong. First of all, RGB is not a color system. There isn't "one
RGB", there is at best a color gamut, and RGB are three primaries picked
arbitrary within the gamut. However, that's a subset of all available
colors, namely everything within the RGB triangle. A popular choice for
primaries are of course red, green and blue, but do not need to be. Any
three linearly independent colors do.
Thus, *a* RGB color space (not *the*...) is the triangle in the XYZ
color gamut spawned by three primaries. These may or may not be red,
green and blue.
Second, CMY (or CMYK) is often referred to as "subtractive" color
format, though this is highly misleading. I would rather call this a
multiplicative color space. In RGB, the output color is generated by
additive mixture (overlay) of colors. In CMY, a white color input
undergoes filtering by three spectral filters. Thus, a C (cyan) filter
would remove red. This is multiplicative because the filter
characteristic of applying two filters (such as C and M) is a filter
whose spectral sensitivity is the pointwise product of the C and M filter.
As for RGB, which primaries you pick is entirely up to you. There is no
need for them to be C, M and Y, though this a popular choice. CMY models
the color reproduction in print - color pigments act as filters, RGB the
color reproduction of displays, where light mixes.
yeah I forget, there is no one RGB or CMY
--
Dale
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