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216 colors (Web Safe)

SmartNote: 1
Type: Term
ColorGeek factor: unrated
See Web-safe colors

See Also

Term: Indexed Color
Term: Web browsers
Term: Cross-platform color
Term: CLUT
Term: Web-safe colors

256 colors

SmartNote: 2
Type: Term
ColorGeek factor: unrated
When a computer?s graphics system uses 8 bits of information to store each pixel in an image, the most effective way of gaining the widest range of colors is to use a Color Look Up Table (CLUT). This is called indexed color. Each pixel can be one of 256 colors (2^8) and the colors are chosen from a palette of 16 million. If the palette is chosen carefully and the image doesn?t have too wide a range of color, you can get a reasonably pleasing result. The choice of pallete, and what your operating system does to it, however can really mess up your images. Both the Mac OS and Windows have standard 256-color palettes (not that same colors of course). They are called the system palettes and were chosen to have the widest application possible. Photoshop can create custom palettes for your images but beware that the system displaying your image may not have access to the custom palette.

See Also

Term: Indexed Color
Term: Bit depth
Term: CLUT

4-color

SmartNote: 3
Type: Term
ColorGeek factor: unrated
A press, press run or printer that applies 4 colors to the paper. For process color the 4 colors are CMYK (Cyan, Magenta, Yellow, and Black).

See Also

Term: Color Separations
Term: CMYK Cyan, Magenta, Yellow, Black
Term: Process color
Term: Spot color

5000K

SmartNote: 4
Type: Term
ColorGeek factor:
5000K has the coordinates for xyY of (0.3457, 0.3585, 100)

See white point

See Also

Term: White point
Term: Blackbody, Black Body Radiation
Term: Color Temperature
Term: D50

6500K

SmartNote: 5
Type: Term
ColorGeek factor:
see white point

See Also

Term: Color Temperature
Term: Blackbody, Black Body Radiation
Term: White point
Term: D65

9300K

SmartNote: 6
Type: Term
ColorGeek factor:
see white point

See Also

Term: Color Temperature
Term: Blackbody, Black Body Radiation
Term: White point

a

SmartNote: 7
Type: Term
ColorGeek factor: unrated
a is the axis in the Lab color space which denotes the ?red-green? component of the image. One end of the axis is green and the other end red. Combined with the b axis, you can describe the hue and saturation of a color.

See Also

Term: CIELab, Lab
Term: b
Term: L

Additive Primary Colors

SmartNote: 8
Type: Term
ColorGeek factor: unrated
Red, Green and Blue are additive primary colors. That is, in an imaging system which creates colors by using light (monitors, file recorders), red green and blue can combine in equal quantities to produce white. All the colors the device is able to create (the device?s gamut) are produced by varying the amounts of red, green and blue.

See Also

Term: RGB
Term: Subtractive primaries

Antialiasing

SmartNote: 9
Type: Term
ColorGeek factor: unrated
Antialiasing is a technique used to smooth the edges of line art, fonts, and other vector art by blending the edges of the object with its background and creating intermediary colors and shades. Technically it lowers the resolution of the image but done correctly, and viewed from sufficient distance, can appear to smooth previously jagged edges and actually increase the apparent resolution. It is a good technique for screen display (CD-ROM and Web publishing) but should not be used for printing in most cases as the higher resolution of a printing device will often reduce jaggies and antialiasing would make it look worse.

See Also

Term: Resolution

b

SmartNote: 10
Type: Term
ColorGeek factor: unrated
b is the axis in the Lab color space which denotes the ?blue-yellow? component of the image. One end of the axis is blue and the other end yellow. Combined with the a axis, you can describe the hue and saturation of a color.

See Also

Term: CIELab, Lab
Term: a
Term: L

Bit depth

SmartNote: 11
Type: Term
ColorGeek factor: unrated
The number of bits which are used to store each pixel in an image. Each additional bit adds twice as many color combinations to the number available. 1 bit (bit-mapped - monochrome), 8bit (indexed color and web-safe color), 16 bit (?thousands of colors?) and 24 bit (?true color?, ?millions of colors?) are common bit depths.
Increasing the bit depth can greatly affect the quality and size of your images.

See Also

Term: Indexed Color

Bitmap

SmartNote: 12
Type: Term
ColorGeek factor: unrated
A raster computer image which is monochrome. Each dot can either be on or off and there are no shades or colors available. It is called a bit map because the bits used to store the image map directly to the dots on the screen 1 to 1.

See Also

Term: Bit depth

Blackbody, Black Body Radiation

SmartNote: 14
Type: Term
ColorGeek factor: unrated
A black body is a theoretical object which absorbs all light which strikes it and emits different wavelengths of light depending on the temperature to which it is heated. The color temperatures of 5000 degrees K, 6500 degrees K, etc all refer to the ?color temperature? of a black body heated to that temperature. Kelvin degrees are similar to degrees Celsius but start 273 degrees lower at absolute zero (0 degrees Celsius - freezing - is 273 degrees Kelvin)

See Also

Term: White point

Brightness

SmartNote: 15
Type: Term
ColorGeek factor: unrated
1) Setting on Monitors - unlike contrast (which should be set to it?s maximum setting in most cases), brightness should be set manually according to your profile software?s instructions. As the phosphors in your monitor fade over time, the amount of light they emit will decrease and you will probably have to turn your brightness up. If you are unable to turn it up to an acceptable level it?s time for a new monitor - give yours to your favorite accountant - they?ll love the size and not care about the color.

2) B component in HSB - The visual attribute by which a color appears to exhibit more or less light. This correlates directly with the amplitude of the light waveform (as opposed to the purity or the wavelength(s))

See Also

Term: HSB

Calibrate, Calibration

SmartNote: 17
Type: Term
ColorGeek factor: unrated
Calibration is the act of returning a device to factory, or some other, known specification. It does not characterize the device in the way a Profile does, but calibration should always be performed prior to building a profile.
Re-calibrating a device sometime after a profile was built should return the device to the state where the profile is valid and can continue to be used.

See Also

Term: Profiling

CCD

SmartNote: 18
Type: Term
ColorGeek factor: unrated
CCD stands for Charge Coupled Device. It is a light sensitive solid-state device that is used in digital cameras, most desktop scanners (and some higher-end ones), colorimeters, video cameras, and other devices. Their dynamic range is improving but is still not up to that of the PhotoMultiplier Tubes used in drum scanners.

See Also

Term: Photo Multiplier Tube - PMT
Term: Digital cameras
Term: Scanners
Term: Dynamic Range

CIELab, Lab

SmartNote: 19
Type: Term
ColorGeek factor:
CIELab is the color space that ICC Profiles and CMMs often use as an intermediary space when converting colors. So a monitor to printer match translates colors from the monitor*s space (RGB) into Lab and then into the printer*s color space (CMYK for example).

The L component is the lightness of the color.
The a component is the red/green scale (+a is red, -a is green)
The b component is the blue/yellow scale (+b is yellow, -b is blue - go figure)

CIELab, or more correctly CIEL*a*b* is a (mostly) device independent color-space based on the measurements of hundreds of humans the CIE made in 1931 when they created the CIEXYZ color space. In 1976 the CIE created the Lab space to reflect the entire gamut or range of colors the human eye can typically see. The Lab space, unlike other CIE color spaces, is supposed to be perceptually uniform. That is, any movement within the space, in any direction, should result in an equally perceptible color shift. There are many who believe that the Lab space is not perceptually uniform but that is outside the scope of this glossary.

LCH is another way of measuring the same color space. (see LCH for more information)

The Lab color space is not precisely device independant as it is defined relative to a reference white point. This white point is often based on the whitest point that can be generated by a device or a standard white point (like D50).

See Also

WebSite: CIE - Commission Internationale De l'Eclairage
Term: CIExyY, xyY
Term: LCH

Chroma

SmartNote: 20
Type: Term
ColorGeek factor: unrated
Chroma is the C component of the LCH color space.

Chroma represents how far out from the center of the color space (radially) a color lies. The farther out the more saturated the color.

The "colorfulness" of a sample judged proportional to the brightness of a white reference sample in the same medium and under the same illumination.

See Also

Term: LCH

Chromaticity Diagram

SmartNote: 21
Type: Term
ColorGeek factor: unrated
The Chromaticity Diagram is a horseshoe-shaped graph of the CIELab color space where the L component has been removed and the a and b components are then graphed in 2 dimensions. It is a very useful diagram for getting a quick feeling for not only the range of colors humans can perceive but the ranges of colors (gamuts) that different devices can (or cannot) display.

See Also

Term: CIELab, Lab

CIE - Commission Internationale De l'Eclairage

SmartNote: 22
Type: WebSite
ColorGeek factor:

Link: http://www.cie.co.at/cie/
(will open in a new browser window)

See Also

Term: CIELab, Lab
Term: CIExyY, xyY

CLUT

SmartNote: 26
Type: Term
ColorGeek factor: unrated
A CLUT is a Color Look Up Table. This is used with indexed color schemes when a lower number of bits are used to store each pixel's color so a look up table is used to increase the number of colors available. See Indexed Color for a more complete description.

See Also

Term: Indexed Color
Term: Bit depth

CMM - Color Matching Method

SmartNote: 27
Type: Term
ColorGeek factor: unrated
The CMM is the "engine" that actually does the work of color management. There are many different CMM's available from vendors such as Linocolor, Kodak, Adobe (within Photoshop), and others. The CMM contains the actual executable code that uses the ICC Profile information supplied by the user to transform the colors of a document.

While the debate may rage on about which CMM is best to use (and that probably differs the most depending on your workflow), one thing most color scientists would agree on is you should choose one CMM and use it throughout your workflow. At this time, in our opinion, this removes the Adobe CMM from most workflows as it is only available within Photoshop (and presumably more Adobe products as time goes on). Unless you do all your color work in one application, you should choose a CMM that is available to all applications.

See Also

Term: CMS Color Management System

CMYK Cyan, Magenta, Yellow, Black

SmartNote: 29
Type: Term
ColorGeek factor: unrated
The four colors commonly used in process color printing. Black is added to CMY to enhance the density of dark areas and solve gray balance problems encountered when trying to make neutral grays with CMY alone.

The letters stand for:

C: Cyan
M: Magenta
Y: Yellow
K: Key Color (which is usually black)

See Also

Term: Subtractive primaries
Term: Process color

Colorimeter

SmartNote: 35
Type: Term
ColorGeek factor: unrated
A device for measuring tri-stimulus values like RGB and XYZ. Colorimeters are often used for monitor calibration and profiling. They read their measurements using three or more filters, and as such are not as accurate as spectrophotometers at measuring the true color characteristics of objects.

See Also

Term: Densitometer
Term: Spectrophotometer

ColorSync

SmartNote: 37
Type: Utility
ColorGeek factor:
ColorSync is Apple?s color management standard and framework which has been built into the Mac OS for years.
ColorSync is a standard method for developers to call the operating system when they want their programs to correctly manage color. There are also provisions in ColorSync that allow developers to write their own Color Matching Methods and also for the users to select different ICC profiles to use. In some sense, ColorSync is the glue that holds it all together, but it is also a standard, one that ships with every copy of Mac OS. That reassures developers, and end users alike that it will be present in their users? systems and solutions can be built around it.

See Also

Term: MacOS
Term: CMM - Color Matching Method
Term: Profile
WebSite: ColorSync Website
TechTip: Profiling Monitors with ColorSync

Colour

SmartNote: 39
Type: Term
ColorGeek factor: unrated
as in the correct spelling ;-)

Contrast

SmartNote: 43
Type: Term
ColorGeek factor: unrated
1) setting on monitors

2) in images

See Also

Term: Monitors

Cross-platform color

SmartNote: 45
Type: Term
ColorGeek factor: unrated
Cross platform color management refers to managing color between different operating systems. Getting your Mac and Wintel monitors to match and your printed output to be the same is a difficult task. Luckly, several things are in place to help, and others are on their way.

- ICC Profiles - are platform-independent by definition. That means you can easily move them from machine to machine.
- Adobe Photoshop 5.x is available on both platforms and implements color management (mostly) the same way on both.

Some things working against you are:

- The gamma settings can be quite different between the Mac and PC. Photoshop can compensate for this when designing, but when displaying on different systems you can have problems.
- Windows does not implement color management on nearly the same scale, nor do as many content creation programs support ICC color management.

See Also

Term: MacOS
Term: UNIX
Term: Windows 98
Term: Windows NT
Term: ICC International Color Consortium
Term: Gamma

Displays

SmartNote: 55
Type: Term
ColorGeek factor: unrated
see monitors

See Also

Term: Monitors

Drum scanners

SmartNote: 56
Type: Term
ColorGeek factor: unrated
see scanners

See Also

Term: Scanners

EMR

SmartNote: 59
Type: Term
ColorGeek factor: unrated
Electromagnetic Radiation. Visible light is one subset of a whole range of radiation called EMR.

See Also

Term: Blackbody, Black Body Radiation

File formats

SmartNote: 62
Type: Term
ColorGeek factor: unrated
Graphics information, when written to disk, can be stored in many different formats. Some formats include compression as an option, and others it is required. Many file types can store additional information along with the graphic. This includes ICC profiles, color palattes, comments, and specifications.

See Also

Term: PICT
Term: EPS
Term: TIFF
Term: PDF
Term: Cross-platform color

Film

SmartNote: 63
Type: Term
ColorGeek factor: unrated
1) for printing

2) photographic for scanning

3) dynamic range of

Indexed Color

SmartNote: 81
Type: Term
ColorGeek factor: unrated
When a computer?s graphics system uses 8 bits of information to store each pixel in an image, the most effective way of gaining the widest range of colors is to use a Color Look Up Table (CLUT). This is called indexed color. Each pixel can be one of 256 colors (2^8) and the colors are chosen from a palette of 16 million. If the palette is chosen carefully and the image doesn?t have too wide a range of color, you can get a reasonably pleasing result. The choice of pallete, and what your operating system does to it, however can really mess up your images. Both the Mac OS and Windows have standard 256-color palettes (not that same colors of course). They are called the system palettes and were chosen to have the widest application possible. Photoshop can create custom palettes for your images but beware that the system displaying your image may not have access to the custom palette.

Ink

SmartNote: 83
Type: Term
ColorGeek factor: unrated
absorption - see dot gain

Spot Color inks are opaque and Process Color inks are transparent.
What does this mean? Well, when you use Spot colors (like Pantone colors) the ink that is applied to the page on the press does not let light through to the paper and so is affected a lot less by the color of the paper. But, when using 3 or 4-color process inks, the ink is transparent (so each ink color is able to modify the light) so the light hitting the page passes through the ink, gets reflected off the page, and then passes through the ink again before it travels to your eyes. This means that the color of the paper stock plays a huge role in determining the final look of your output.

It also means that spot colors emulated on a 4-color proofing device are affected by the proofing stock much more than they will be on the final press output. Nasty!
What do I do about it? A well-made printer profile should take paper stock color into consideration but you should note that the Rendering Intent you select will or will not correct for the stock color? choose this carefully.

See Also

Term: Dot Gain
Term: Rendering Intent

L

SmartNote: 88
Type: Term
ColorGeek factor: unrated
The L component in Lab and HSL color spaces is the lightness of the color.

See Also

Term: CIELab, Lab
Term: HSL - Hue Saturation and Lightness

Luminance

SmartNote: 94
Type: Term
ColorGeek factor: unrated
Luminance is the brightness component of colors described in the Lab color space.

Is often expressed in Candelas per square meter (cd/m^2)

See Also

Term: CIELab, Lab

Process color

SmartNote: 119
Type: Term
ColorGeek factor: unrated
Process color refers to the inks and process used when a wide range of colors are reproduced using a limited number of inks.

CMYK is the most common process ink set. Cyan, Magenta, Yellow, and black(Key) inks are combined in varying amounts to produce a reasonably wide range of colors. This is much cheaper than using a different ink for every color required and in the case of continuous-tone images like photographs, makes printing in color possible.

See Also

Term: Ink
Term: Spot color
Term: CMYK Cyan, Magenta, Yellow, Black
Term: Subtractive primaries

Profile

SmartNote: 120
Type: Term
ColorGeek factor: unrated
A file containing the colorimetric description of an input or output device in terms useful to a color management system.

See Also

Term: ICC International Color Consortium
Term: Embedding profiles
Term: Profiling
Term: ProfileCentral
Term: Workflow

Resolution

SmartNote: 128
Type: Term
ColorGeek factor: unrated
Resolution has at least two meanings.

1) The correct meaning, used by physicists, biologists, and the scientific world in general, refers to the number of objects within a certain defined physical space. So in the publishing world it usually refers to Dots Per Inch (dpi), Pixels per Inch (ppi) , Lines Per Inch (lpi) or some other similar measurement.

2) The incorrect but very heavily used meaning, which is the size of an image or display. To say a display's resolution is 640 pixels by 480 pixels is common, but not really correct. Now if you said it was showing those dimensions at 72dpi, then you'd be correct.

Now what is the difference between dpi, ppi and lpi? Dots refer to spots of ink, toner, or some other colorant on a piece of paper. They are the smallest dot that can be applied by that device and are usually monochromatic (they are either there or not, you don't have shades to choose from). Pixels (which is short for "picture element") refers to spots which appear on monitor screens. They can be one of a multitude of shades.

What's the difference? Well, a pixel (of many shades) cannot be represented by a dot (of one shade) on a printer. So the printer gathers a whole bunch of dots together into a "cell" and, by varying the number of dots applied in that cell, can simulate a number of shades. If you want to simulate more shades, you need more dots in each cell. The number of cells per inch is called lines per inch (lpi) and is obviously not as many as there are dots per inch. What this means is that if you want your printer to output a continuous-tone image, you are going to have far fewer lines per inch than the say 600 or 1200 dpi you to which you are accustomed.

See Also

Term: File formats
Term: Compression
Term: Bit depth
Term: Halftone
Term: Scanning

RGB

SmartNote: 129
Type: Term
ColorGeek factor: unrated
Red, Green and Blue are additive primary colors. That is, in an imaging system which creates colors by using light (monitors, file recorders), red green and blue can combine in equal quantities to produce white. All the colors the device is able to create (the device?s gamut) are produced by varying the amounts of red, green and blue.

See Also

Term: Additive Primary Colors
Term: Digital cameras
Term: Scanners
Term: Monitors

sRGB

SmartNote: 130
Type: Term
ColorGeek factor: unrated
sRGB is a ?device independent? RGB space which was proposed and adopted by Microsoft and Hewlett Packard as a standard color space for ?the average user?. It is supposed to represent the gamut of the ?average user?s? monitor. Problems associated with this include:

- There is no such thing as an average user - especially with the high-end displays used by graphics professionals
- There is no average monitor
- Adobe, presumably due to the fact that they could not get Microsoft?s ?Windows Compatible? certification without it, set sRGB as the default color space within Photoshop 5.0. Thankfully they updated PS to 5.0.2 which included a ?wizard? which guided the user in setting up PS and hopefully the user avoids this color space altogether.

sRGB is not all bad. The basic idea of converting images to sRGB which are headed to the web (and when the audience is the general public) makes sense. In many cases, supplying a large profile with each image does not make for a speedy web site. With sRGB, no profile is required and a properly tuned system on the user?s end will display the image correctly.

The sRGB also has a gamma of 2.2. This can cause display issues on monitors set to other gammas (like Mac OS systems, which are often set @ 1.8)

See Also

Term: Web browsers
WebSite: sRGB Website
Article: sRGB - Microsoft?s Explanation
Term: RGB
Term: Gamma
Term: Device-Independent Color

Saturation

SmartNote: 133
Type: Term
ColorGeek factor: unrated
The colorfulness of a sample compared to its brightness, where colorfulness is defined as lack of white, gray or black components.

See Also

Term: HSB
Term: HSL - Hue Saturation and Lightness

Spectrophotometer

SmartNote: 137
Type: Term
ColorGeek factor: unrated
A device for measuring luminous energy at many frequencies throughout the spectrum. Spectral data can usually be displayed in convenient units such as CMY density, L*a*b* or XYZ.

See Also

Term: Densitometer
Term: Colorimeter
Term: Profiling
Term: CIExyY, xyY

Spot color

SmartNote: 139
Type: Term
ColorGeek factor: unrated
Spot color refers to colors in an image which are created with a specific ink formulation rather than a combination of inks like in process color.

One of the more popular spot color ink sets is the Pantone Matching System. Pantone has created a series of inks which can be used with high reliability in a projects where you know you have additional plates available to you. (don't try to use spot colors in newspapers for instance, the chances of the press operator loading another plate just for your logo on page 27 is remote indeed)

See Also

Term: Ink
Term: Process color
Term: Color Separations

Stock

SmartNote: 140
Type: Term
ColorGeek factor: unrated
The paper stock on which you print can have a major effect on your output. Stock comes in many forms and can range from newsprint all the way to plastic film. How inks are act when applied to paper is a complex issue and worthy of some discussion. There are several points worth considering:

Spot Color inks are opaque and Process Color inks are transparent.
What does this mean? Well, when you use Spot colors (like Pantone colors) the ink that is applied to the page on the press does not let light through to the paper and so is affected a lot less by the color of the paper. But, when using 3 or 4-color process inks, the ink is transparent (presumably so each ink color is able to modify the light) so the light hitting the page passes through the ink, gets reflected off the page, and then passes through the ink again before it travels to your eyes. This means that the color of the paper stock plays a huge role in determining the final look of your output.
It also means that spot colors emulated on a 4-color proofing device are affected by the proofing stock much more than they will be on the final press output. Nasty!
What do I do about it? A well-made printer profile should take paper stock color into consideration but you should note that the Rendering Intent you select will or will not correct for the stock color? choose this carefully.

Ink Absorption and Dot Gain
If the stock you are using is absorbent and the inks are liquid (as opposed to wax or toner as in many proofing printers) then the ink will "wick" into the paper as it is applied. This makes the dots fuzzier and larger and is one of the contributors to Dot Gain. For example, if you print a 10% cyan square on the page and then take a reading of the square with a Densitometer, you may find that it is in fact a 15% cyan square. This means your printer or press has a 5% dot gain.
What do I do about it? Again, a printer profile should automatically take dot gain into consideration and compensate for it. This is yet another reason to profile for every paper stock you use, as each one will affect ink differently.

See Also

Term: Ink
Term: Dot Gain

Subtractive primaries

SmartNote: 141
Type: Term
ColorGeek factor: unrated
Cyan, Magenta, and Yellow are subtractive primary colors. That is, in an imaging system which creates colors by using inks or other pigments (printers, presses, some proofing systems), cyan, magenta and yellow can combine in equal quantities to produce black (actually muddy brown in most cases - that's one of the reasons black is usually used). All the colors the device is able to create (the device?s gamut) are produced by varying the amounts of each ink color.

Subtractive colors get their name because they are thought of as subtracting light out of an image. Cyan, for instance subtracts (absorbs) red light. If less red is required in a color, more cyan ink is added.

See Also

Term: CMYK Cyan, Magenta, Yellow, Black
Term: Additive Primary Colors
Term: RGB

Tri-stimulus, Tristimulus

SmartNote: 155
Type: Term
ColorGeek factor: unrated
Values The quantities of red, green and blue lights of specific wavelengths and bandwidths needed to match a certain color.

See Also

Term: RGB
Term: HSB
Term: HSL - Hue Saturation and Lightness

UCR

SmartNote: 156
Type: Term
ColorGeek factor: unrated
Under Color Removal. The reduction of CMY percentages in dark pixels to limit the total ink printed in shadows. UCR is set by specifying a "Total Dot Percentage" (TDP) and "maximum black dot" from which UCR is calculated automatically.

See Also

Term: Process color
Term: Color Separations
Term: Profiling

Web browsers

SmartNote: 164
Type: Term
ColorGeek factor: unrated
Web browsers can affect the way color is viewed by your end user. Designed for speedy display, they aren't often optimized for image fidelity. Combine that with web designers who, understandably, squash images to their smallest size and you end up with poor image quality on many web sites.

Microsoft's Internet Explorer has supported ColorSync on the Mac since version 4.x. At this time, Netscape still does not support ColorSync (as of version 4.5). This does not mean you cannot manage color going to the web, you just have much less control.

To tag images (include profiles) that are going to the web, HTML commands are available. See the following links for more information:

See Also

Term: Web-safe colors
Term: Cross-platform color
Term: Workflow
Term: sRGB
Article: ICC Profiles in HTML