DIGITAL FORMATS FOR PUBLICATION
© Kansas City Artists Coalition
DIGITAL COLOR
Screen (web, e-mail) |
|
transmitted light |
reflected light |
RGB color space (gamut) additive light theory |
CMYK color space (gamut) subtractive light theory |
Red + Green + Blue = White |
Cyan + Magenta + Yellow = Black |
Green + Blue - Red = |
Cyan |
Indexed color and web safe colors |
Pantone Matching System - printing standard in the US |
Note: Once you change an image to CMYK color space, you cannot change back to RGB color space.
ANATOMY OF A DIGITAL IMAGE
Pixels (picture element) are square. A bitmap is a map of pixels. The binary digits 1 and 0 equal 1 bit. 1 bit = 2 levels.
2 bit = 4 levels.
8 bit = 256 levels. 8 bits = 1 byte.
1024 bytes = 1 kilobyte KB. 1024 kilobytes = 1 megabyte MB. 1024 megabytes = 1 gigabyte GB. RGB is 24 bit color while CMYK is 32 bit color. Mac's describe colors in "millions of colors" while
PC's talk about "true color".
GAMMA
A monitor setting that effects the overall contrast and brightness. It is important to review images for the Web on both Mac and PC because they have a different gamma standard. 1.8 is the standard gamma for Mac while 2.2 is the standard gamma for PC. Note: This means that images created on a Mac, when opened on a PC, will look darker and will have less contrast and vice versa for images created on a PC and opened on a Mac. Keep this in mind when preparing images for web or screen use. On both Mac's and PC's you can change the gamma setting to simulate what you images will look like on another computer.
COLOR PROFILES
A color profile, also called "device profile", or simply "profile", refers to the relationship between the color models of the system devices. In Photoshop a color profile can be assigned when saying the image and can be changed or reassigned using the Image/Mode/Assign Profile or Convert to Profile command.
COLOR SPACE
sRGB stands for standard RGB. It is referred to as "standard" because it has been agreed upon by several large players - Apple, Adobe, Microsoft, Hewlett Packard, etc. It is one of several RGB working spaces but is best used for the Web and not for print.
FILE FORMATS
Native Photoshop (.psd)
TIFF Tagged Image File Format (.tif)
PDF Portable Document File (.pdf).
Note: when naming files always use the file extension and the 8.3 rule. This means that you should try to keep file names 8 characters or shorter and type your file extension. Not all programs will support long file names.
IMAGE COMPRESSION
JPEG Joint Photographer's Expert Group: lossy compression (.jpg)
ZIP (PC) and StuffIt (Mac): lossless compression
LZW Lemple-Zif-Welch: lossless compression
Note: Use TIFF for print use and JPEG for screen or web use.
REFERENCES
Complete Guide To Digital Color: Creative Use of Color In The Digital Arts, by Chris Linford. ©2004 Axis Publishing Ltd. ISBN 0-06-072793-4
Mastering Digital Printing, Second Edition. The Photographer's and Artist's Guide to High Quality Digital Output by Harald Johnson. ©2004 Muska & Lipman Publishing. ISBN 1-59200-431-8
Real World Color Management, Second Edition. Industrial-Strength Production Techniques by Bruce Fraser, Chris Murphy, and Fred Bunting. ©2005 Peachpit Press. ISBN 0-321-26722-2
Total Digital Photography: The Shoot To Print Workflow Handbook by Serge Timacheff and David Karlins. ©2005 Wiley Publishing, Inc. ISBN 0-7645-6952-X