問72
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光の三原色の説明として, 適切なものはどれか。
平成24年度 春期 ITパスポート試験 問72
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This question's explanation and your answers so far.
解説
問 72
Incorrectア
Cyan (Cyan), magenta (Magenta), and yellow (Yellow) are the “three primary colors of color (coloring materials)”, not the three primary colors of light. They are used in “subtractive color mixing”, as with ink or paint, where overlaying more of them removes more of the reflected light and makes the result darker, and overlaying all three theoretically approaches black. The CMYK of a printer adds black (Key plate) to this CMY. Making the reader confuse light = additive mixing (RGB) with coloring materials = subtractive mixing (CMY) is the central trap of this question.
Incorrectイ
Hue (Hue), saturation (Saturation), and brightness (Brightness) are the “three attributes of color”, the three elements of the HSB (HSV) family of color models that express a color numerically. They do not list three colors themselves; they are a framework that expresses a single color by three measures, namely what kind of hue it has, how vivid it is, and how bright it is. It is therefore wrong as a description of the three primary colors. The three primary colors (a combination of primary colors) and the three attributes (a way of measuring color) are different concepts.
Incorrectウ
Red and green are indeed among the three primary colors of light, but the third one is given as yellow, which is the mistake; it should be blue. Yellow is not a primary color of light but a color obtained by overlaying red and green light (a secondary color of additive mixing), and it is at the same time one of CMY, the three primary colors on the coloring-material side. Because two of the three are right it is easy to pick, but recalling that a primary color is a color that cannot be made from a combination of the other primary colors lets you rule it out.
- エ
正解 The three primary colors of light are the three colors red (Red), green (Green), and blue (Blue), that is, RGB, so エ is correct. Light follows “additive color mixing”, in which the more colors are overlaid the brighter the result: overlaying R, G, and B at equal intensity gives white, while shining none of them gives black (no light). Another feature of additive mixing is that overlaying two of them at a time produces the primary colors of the coloring-material side: R and G give yellow, G and B give cyan, and B and R give magenta. Devices that emit or receive light themselves, such as displays, projectors, and the image sensors of digital cameras, express color in units of this RGB, and the 24-bit color notation used on the Web likewise represents R, G, and B with 8 bits each.
ここがポイント
- The three primary colors of light are R (Red), G (Green), and B (Blue), and they follow additive color mixing, where overlaying more of them makes the result brighter. Overlaying all three in equal amounts gives white, and this is used in devices that handle light, such as displays and digital cameras.
- The three primary colors of color (coloring materials) are C (Cyan), M (Magenta), and Y (Yellow), and they follow subtractive color mixing, where overlaying more of them makes the result darker. Printing uses CMYK, which adds black. Overlaying two of RGB produces a CMY color, and overlaying two of CMY produces an RGB color, so the two sets are in a complementary-color relationship.
- Hue, saturation, and brightness are the three attributes of color, a different concept from the three primary colors. Keep in mind that a primary color is a “color that cannot be produced even by mixing the other primary colors”.
用語