Digital image processing
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The document discusses the YMC (Yellow-Magenta-Cyan) color model, also known as the CMYK color model. It is a subtractive color model used in printing. The CMYK color model uses the four process colors (cyan, magenta, yellow, and key (black)) to print a range of colors by partially or entirely masking the white background with ink. Halftoning allows less than full saturation of the primary colors, producing a continuous range of colors perceived by the human eye. Using black ink in addition to CMY is more cost effective and produces deeper blacks and more accurate reproduction of text.
Digital image processing
- 2. INTRODUCTION YMC stands for Yellow - Magenta - Cyan Also known as CMYK i.e. : cyan, magenta, yellow and key (black) It is a colour model basically a subtractive colour model used in printing press
- 3. COLOUR MODEL Colour Model- A mathematical model of colours with different shades and hues. Definition- It is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. Mainly this section describes ways in which human color vision can be modeled. Color effects are due to contrasts on three relative attributes that define all colors: lightness (light vs. dark, or white vs. black), saturation (intense vs. dull), and hue (e.g. red, orange, yellow, green, blue or purple)
- 4. COLOUR MODEL DIVISION Colour model is further divided into two types: Additive colour Model i.e. RGB colour model Subtractive colour model i.e. YMC colour model
- 5. RGB V/S YMC RGB- Additive color systems start with darkness. Light sources of various wavelengths are added in various proportions to produce a range of colors. Usually, three primary colors are combined to stimulate humans’ trichromatic color vision, sensed by the three types of cone cells in the eye, giving an apparently full range. YMC- Subtractive color systems start with light, presumably white light. Colored inks, paints, or filters between the watchers and the light source or reflective surface subtract wavelengths from the light, giving it color. If the incident light is other than white, our visual mechanisms are able to compensate well, but not perfectly, often giving a flawed impression of the "true" color of the surface.
- 6. YMC COLOUR MODEL CMYK refers to the four inks used in some color printing: cyan, magenta, yellow and key (black). The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks "subtract" brightness from white. In additive color models such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta and yellow.
- 7. HALFTONING With CMYK printing, halftoning (also called screening) allows for less than full saturation of the primary colors; tiny dots of each primary color are printed in a pattern small enough that human beings perceive a solid color. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots on the large white paper as lighter and less saturated than the color of pure magenta ink. Without halftoning, the three primary process colors could be printed only as solid blocks of color, and therefore could produce only seven colors: the three primaries themselves, plus three secondary colors produced by layering two of the primaries: cyan and yellow produce green, cyan and magenta produce blue, yellow and magenta produce red (these subtractive secondary colors correspond roughly to the additive primary colors) plus layering all three of them resulting in black. With halftoning, a full continuous range of colors can be produced.
- 8. BENEFITS OF USING BLACK INK The "black" generated by mixing commercially practical cyan, magenta and yellow inks is unsatisfactory, so four-color printing uses black ink in addition to the subtractive primaries. Common reasons for using black ink include: In some cases a black keyline was used when it served as both a color indicator and an outline to be printed in black Text is typically printed in black and includes fine detail (such as serifs), so to reproduce text or other finely detailed outlines, without slight blurring, using three inks would require impractically accurate registration A combination of 100% cyan, magenta, and yellow inks soaks the paper with ink, making it slower to dry, causing bleeding, or (especially on cheap paper such as newsprint) weakening the paper so much that it tears Using black ink is less expensive than using the corresponding amounts of colored inks The amount of black to use to replace amounts of the other ink is variable, and the choice depends on the technology, paper and ink in use. Processes called under color removal, under color addition, and gray component replacement are used to decide on the final mix; different CMYK recipes will be used depending on the printing task
- 9. OTHER PRINTER COLOR MODELS Some printing presses are capable of printing with both four-color process inks and additional spot color inks at the same time. High-quality printed materials, such as marketing brochures and books, may include photographs requiring process-color printing, other graphic effects requiring spot colors (such as metallic inks), and finishes such as varnish, which enhances the glossy appearance of the printed piece. They have further model division of YMC model: Pantone's proprietary six-color (CMYKOG) Hexachrome considerably expand the gamut for better color reproduction. Light, saturated colors often cannot be created with CMYK, and light colors in general may make visible the halftone pattern CcMmYK process, with the addition of light cyan and magenta inks to CMYK, can solve these problems, and such a process is used by many inkjet printers, including desktop models