The difference between RBG and CMYK

CMYK

The CMYK model is based on the light-absorbing quality of ink printed on paper. As white light strikes translucent inks, part of the spectrum is absorbed and part is reflected back to your eyes. In theory, pure cyan (C), magenta (M), and yellow (Y) pigments should combine to absorb all color and produce black. For this reason these colors are called subtractive colors. Because all printing inks contain some impurities, these three inks actually produce a muddy brown and must be combined with black (K) ink to produce a true black. (K is used instead of B to avoid confusion with blue.) Combining these inks to reproduce color is called four-color process printing.

We recommend the CMYK model for all full-color images.


RGB
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.

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.

Proper reproduction of colors, especially in professional environments, requires color management of all the devices involved in the production process, many of them using RGB. Color management results in several transparent conversions between device-independent and device-dependent color spaces (RGB and others, as CMYK for color printing) during a typical production cycle, in order to ensure color consistency throughout the process. Along with the creative processing, such interventions on digital images can damage the color accuracy and image detail, which can change the expected color when printed on a four-color press.

Submitting work for print in RGB color modes can often result in changes in color when printed.  As a result, we always prefer that documents are submitted in CMYK color. 

 
 
 
 
IMAGE FORMATS PRIMER

 
 




Encapsulated PostScript (EPS) language file format can contain both vector and bitmap graphics and is supported by virtually all graphic, illustration, and page-layout programs. EPS format is used to transfer PostScript-language artwork between applications.
We recommend EPS graphics for vector and bitmap images.


 
 





Tagged-Image File Format (TIFF) is used to exchange files between applications and computer platforms. TIFF is a flexible bitmap image format supported by virtually all paint, image-editing, and page-layout applications. Also, virtually all desktop scanners can produce TIFF images.
We recommend TIFF graphics for bitmap images.


 
  Joint Photographic Experts Group (JPEG) format is commonly used to display photographs and other continuous-tone images in hypertext markup language (HTML) documents over the World Wide Web and other online services. JPEG format supports CMYK, RGB, and Grayscale color modes, and does not support alpha channels. Unlike GIF format, JPEG retains all color information in an RGB image but compresses file size by selectively discarding data.
Due to the fact the the JPEG format discards data, we do not recommend it for any images.
If you must use the JPEG format, please make sure all quality settings are at their maximum and the resolution is at least 300 dpi.


 
  BMP is a standard Windows image format on DOS and Windows-compatible computers. BMP format supports RGB, Indexed Color, Grayscale, and Bitmap color modes, and does not support alpha channels.
We DO NOT recommend the BMP format for any images.



 
  PICT format is widely used among Mac OS graphics and page-layout applications as an intermediary file format for transferring images between applications. PICT format supports RGB images with a single alpha channel, and indexed-color, grayscale, and Bitmap-mode images without alpha channels. PICT format is especially effective at compressing images with large areas of solid color. This compression can be dramatic for alpha channels with their large areas of white and black.
We DO NOT recommend the PICT format for any images.


 
  Graphics Interchange Format (GIF) is the file format commonly used to display indexed-color graphics and images in hypertext markup language (HTML) documents over the World Wide Web and other online services. GIF is an LZW-compressed format designed to minimize file size and electronic transfer time. GIF format preserves transparency in indexed-color images; however, it does not support alpha channels.
We DO NOT recommend the GIF format for any images.


 
Vector Graphics vs. Bitmap Graphics


Vector Graphics
Vector graphics are made up of lines and curves defined by mathematical objects called vectors. Vectors describe an image according to its geometric characteristics. For example, a bicycle tire in a vector graphic is made up of a mathematical definition of a circle drawn with a certain radius, set at a specific location, and filled with a specific color. You can move, resize, or change the color of the tire without losing the quality of the graphic.

Vector graphics are resolution-independent—that is, they can be scaled to any size and printed at any resolution without losing detail or clarity. As a result, vector graphics are the best choice for representing bold graphics that must retain crisp lines when scaled to various sizes—for example, logos.


Bitmap Graphics
Bitmap images—technically called raster images—use a grid of colors known as pixels to represent images. Each pixel is assigned a specific location and color value. For example, a bicycle tire in a bitmap image is made up of a mosaic of pixels in that location. When working with bitmap images, you edit pixels rather than objects or shapes.

Bitmap images are the most common electronic medium for continuous-tone images, such as photographs or digital paintings, because they can represent subtle gradations of shades and color. Bitmap images are resolution-dependent—that is, they contain a fixed number of pixels. As a result, they can lose detail and appear jagged if they are scaled on-screen or if they are printed at a lower resolution than they were created for.

 
 
 
 
File Compression


When downloading items or sending artwork to us, you'll need a utility to compress and decompress your files. Compressing and archiving files together can make them substantially smaller in size, resulting in saved disk space, quicker transmission times and easier file management. If you're looking for a specific file compression utility, chances are that it appears below.




MacRAR™
MacRAR is a shareware RAR file compression utility for the Mac. It features drag-and-drop support, an appearance manager and navigation services. It also has AppleHelp documentation, information on archived items and on the archive itself.


MacZip
MacZip is a freeware tool that supports PKZip compression and extraction. MacZip can compress files for Mac, Windows, Unix and others. It also supports data encryption for secure archiving.


StuffIt Deluxe
The Mac version of the popular cross-platform compression utility, StuffIt Deluxe supports all popular compression standards, including Zip, RAR, SIT and many more. The utility features lossless compression, 512-bit data encryption, password protection, advanced archiving and catalog capabilities and archive splitting for ease of file transfer.




ALZip™
ALZip is a freeware archiving and compression utility designed for speed and ease of use. It supports 36 archive and compression file formats including Zip, opens CD image files (ISO, BIN), opens virtual CD files (LCD), creates eight archive and compression file formats, creates self-extracting files and splits compressed files for easy transfers.


StuffIt Deluxe©
The Windows version of the popular cross-platform compression utility, SuffIt Deluxe supports all popular compression standards, including Zip, RAR, SIT and many more. The utility features lossless compression, 512-bit data encryption, password protection, advanced archiving and cataloging capabilities, and archive splitting for ease of file transfer.


WinRAR®
WinRAR is a shareware file compression utility that features the ability to process non-RAR archive formats including Zip files, support for long filenames, self-extracting archives, the repair of damaged archives, authenticity verification and encryption.


WinZip®
WinZip is the popular compression utility for the Windows environment. Its tight integration with Windows and its optional wizard interface makes file compression quick and easy. In addition to support for the Zip standard, WinZip features support for RAR, CAB, TAR, gzip and other standards.



GNU gzip
The popular GNU Zip compression utility. It is commonly used with TAR to provide an excellent archiving format.


StuffIt®
The Linux version of the popular cross-platform compression utility, StuffIt supports all popular compression standards, including Zip, RAR, SIT and many more. The utility features lossless compression, 512-bit data encryption, password protection, and archive splitting for ease of file transfer.


The Cool Zippi Tool
An X-Forms-based compression utility that supports eight different compression formats, including Zip, gzip, bzip2, *nix Compress, tar, tar+gzip, tar+bzip2 and tar+Compress.