Glossary 3 Flashcards
specular highlight
A specular highlight is the bright spot of light that appears on shiny objects when illuminated (for example, see image at right). Specular highlights are important in 3D computer graphics, as they provide a strong visual cue for the shape of an object and its location with respect to light sources in the scene.
The term specular means that light is perfectly reflected in a mirror-like way from the light source to the viewer. Specular reflection is visible only where the surface normal is oriented precisely halfway between the direction of incoming light and the direction of the viewer; this is called the half-angle direction because it bisects (divides into halves) the angle between the incoming light and the viewer. Thus, a specularly reflecting surface would show a specular highlight as the perfectly sharp reflected image of a light source. However, many shiny objects show blurred specular highlights.
The three aspects of color are:
Hue
Saturation (aka chroma, intensity, or colorfulness)
Brightness (aka lightness, value, or tone)
Variations in value are also called tints and shades, a tint being a yellow or other hue mixed with white, a shade being mixed with black
RGB in relation to yellow
Red, green and blue lights, representing the three basic additive primary colors of the RGB color system, red, green, and blue. Pure yellow light is composed of equal amount of red and green light.
The color box at right shows the most intense yellow representable in 8-bit RGB color model; yellow is a secondary color in an additive RGB space.
This color is also called color wheel yellow. It is at precisely 60 degrees on the HSV color wheel, also known as the RGB color wheel (Image of RGB color wheel:). Its complementary color is blue.
Yellow (CMYK) (process yellow) (canary yellow)
Cyan, magenta, and yellow are the three subtractive primary colors used in printing. Process yellow (also called pigment yellow or printer's yellow), also known as canary yellow, is one of the three colors typically used as subtractive primary colors, along with magenta and cyan.
Process yellow is not an RGB color, and in the CMYK color model there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer’s ink, so there can be variations in the printed color that is pure yellow ink.
The first recorded use of canary yellow as a color name in English was in 1789.[4]
CMYK color model
The CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black). Though it varies by print house, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.
The “K” in CMYK stands for key because in four-color printing, cyan, magenta, and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. Some sources suggest that the “K” in CMYK comes from the last letter in “black” and was chosen because B already means blue.[1][2] However, this explanation, although useful as a mnemonic, is incorrect.[3]
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 money 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.
Half-toning
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.
Benefits of using black ink in CMYK models
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:[6]
In traditional preparation of color separations, a red keyline on the black line art marked the outline of solid or tint color areas. In some cases a black keyline was used when it served as both a color indicator and an outline to be printed in black. Because usually the black plate contained the keyline, the K in CMYK represents the keyline or black plate, also sometimes called the key plate.
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, and sometimes impractically so. This also can cause the ink to bleed.
Although a combination of 100% cyan, magenta, and yellow inks should, in theory, completely absorb the entire visible spectrum of light and produce a perfect black, practical inks fall short of their ideal characteristics and the result is actually a dark muddy color that does not quite appear black. Adding black ink absorbs more light and yields much better blacks.
Using black ink is less expensive than using the corresponding amounts of colored inks.
When a very dark area is desirable, a colored or gray CMY “bedding” is applied first, then a full black layer is applied on top, making a rich, deep black; this is called rich black.[7] A black made with just CMY inks is sometimes called a composite black or process black.
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.[citation needed]
CMKY vs RGB
Comparisons between RGB displays and CMYK prints can be difficult, since the color reproduction technologies and properties are very different. A computer monitor mixes shades of red, green, and blue to create color pictures. A CMYK printer instead uses light-absorbing cyan, magenta and yellow inks, whose colors are mixed using dithering, halftoning, or some other optical technique. Similar to monitors, the inks used in printing produce a color gamut that is “only a subset of the visible spectrum” although both color modes have their own specific ranges. As a result of this items which are displayed on a computer monitor may not completely match the look of items which are printed if opposite color modes are being combined in both mediums.[9] When designing items to be printed, designers view the colors which they are choosing on an RGB color mode (their computer screen), and it is often difficult to visualize the way in which the color will turn out post printing because of this.
RGB color model
The RGB color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.
The main purpose of the RGB color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. Before the electronic age, the RGB color model already had a solid theory behind it, based in human perception of colors.
RGB is a device-dependent color model: different devices detect or reproduce a given RGB value differently, since the color elements (such as phosphors or dyes) and their response to the individual R, G, and B levels vary from manufacturer to manufacturer, or even in the same device over time. Thus an RGB value does not define the same color across devices without some kind of color management.
Typical RGB input devices are color TV and video cameras, image scanners, video games, and digital cameras. Typical RGB output devices are TV sets of various technologies (CRT, LCD, plasma, etc.), computer and mobile phone displays, video projectors, multicolor LED displays, and large screens such as JumboTron. Color printers, on the other hand, are not RGB devices, but subtractive color devices (typically CMYK color model).
This article discusses concepts common to all the different color spaces that use the RGB color model, which are used in one implementation or another in color image-producing technology.
Additive primary colors (RGB)
(read the rest of the article on RGB - this is just a bit)
To form a color with RGB, three colored light beams (one red, one green, and one blue) must be superimposed (for example by emission from a black screen, or by reflection from a white screen). Each of the three beams is called a component of that color, and each of them can have an arbitrary intensity, from fully off to fully on, in the mixture.
The RGB color model is additive in the sense that the three light beams are added together, and their light spectra add, wavelength for wavelength, to make the final color’s spectrum.[1][2]
Zero intensity for each component gives the darkest color (no light, considered the black), and full intensity of each gives a white; the quality of this white depends on the nature of the primary light sources, but if they are properly balanced, the result is a neutral white matching the system’s white point. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, more or less saturated depending on the difference of the strongest and weakest of the intensities of the primary colors employed.
When one of the components has the strongest intensity, the color is a hue near this primary color (reddish, greenish, or bluish), and when two components have the same strongest intensity, then the color is a hue of a secondary color (a shade of cyan, magenta or yellow). A secondary color is formed by the sum of two primary colors of equal intensity: cyan is green+blue, magenta is red+blue, and yellow is red+green. Every secondary color is the complement of one primary color; when a primary and its complementary secondary color are added together, the result is white: cyan complements red, magenta complements green, and yellow complements blue.
The RGB color model itself does not define what is meant by red, green, and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green, and blue primaries are defined, the color model then becomes an absolute color space, such as sRGB or Adobe RGB; see RGB color spaces for more details.
setting white levels and there is nothing white or black in the scene, you just set the
skin tone
our brains are programmed to know three colors:
blue sky
green grass
skin tone
grayscale (exposure) value/level of skin types:
caucasian women 50-70% caucasian men 45-65% asian/hispanic men 35-50% black men 15-35% black women 20-40%
to set grayscale (exposure) level for a photo where there is nothing white or black in the scene:
Go to inspector Show crop Crop until you just have a box of representative skin tone (If you can't crop in enough, click in the numbers, because the numbers will go farther than the slider will) Go to Corrections Go to Exposure
Color correction is also known as color _______ or color ______
Color correction—also known as color grading or color timing
