With so many acrynoms out there it can be confusing. Here’s an attempt to put some meaning to all those letters.
CMYK – stands for: Cyan, Magenta, Yellow, Black.
This is the color mode/standard for offset printing. Offset printing is quality color printing – like a brochure, or magazine. This is not the type of thing you print off your laser or ink jet printer. It’s not the type of printing that “Kinkos” does. Cyan, magenta, yellow and black are the actual ink colors used and put on paper. Most everything that is printed in full color is actually printed using these four colors. Look closely at anything printed, it’s made-up of tiny dots of these colors. It is the overlapping and varying size of the dots that give the appearance of all the colors that humans can see. Since offset printing is high quality printing it requires quality images and files – which translates to high resolution. Typically the minimum resolution needs to be 300 dpi (dots per inch) at 100% of the size you’re printing. I’ll explain more about printing and resolution in another article. But you should know that if you intend to have anything offset printed, your files (and all images used) need to be saved in the CMYK color mode. If you don’t do it, your printer may charge you for them to do it.
RGB – stands for: Red, Green, Blue.
This is the color mode of reflective colors. In other words these are the colors used for viewing on things like computer monitors and televisions. If you were to take a magnifying glass and look at your computer screen or TV you’d see only these three colors. Most color digital files – like the pictures from your digital camera – are defaultly saved in this color mode. Your laser and ink jet printer will print these files just fine. (Laser and ink jets will print CMYK files as well.)
Unless you are offset printing your files you don’t necessarily need to be concerned with which color mode your files are in, however, it’s always good to ask a vendor which format they prefer whenever you are having something printed – signs, digital posters, laser or ink jet flyers, logos on mugs etc – because some vendors prefer one color mode over another. As stated above, supply the wrong color mode and you may encounter additional charges from that vendor.
PDF – stands for: Portable Document Format.
Developed by Adobe, this format is a nice way to send files to anyone you’d like viewing them who may not have the software you used to develop that file. Typically Adobe Acrobat Reader is required software to view these files, but is standard software and preloaded on most computers. It’s also available for free if necessary. Most software used – such as Microsoft Word – allow you to “save as” or “export as” a PDF document. You will have the option of quality when saving. The higer the quality, the larger the file size. If you are offset printing your document – first save everything in CMYK color mode – then save a “Press Quality” pdf document to send to the printer. If you have a lot of photos it can be a pretty large file size so only use this setting if you are indeed sending it to a printer otherwise the lower “Print Quality” settings are all fine for both viewing on a computer screen as well as printing on a laser or ink jet printer.
JPG – stands for: Joint Photographic Experts Group.
This format is named after the folks who developed it. This is a compression file format. It actually uses what’s known as a “lossy” compression scheme which means that it sacrifices image quality to lower the file size (versus – say – a zip compression). You can control the amount of compression – and thereby file size – when saving as a jpg. But remember, the higher the compression, the lower the quality of the image. An even more important thing to know – you can never regain that quality. So, although this is the current standard for saving large images – this is the default format for your digital camera images – be careful about saving at high compression.
This format is also one of the more standard formats for web use. One reason it was developed was with that intention. The slower bandwidths of years past is why it was important to get files as small as possible – even at the cost of better viewing quality – but nowadays keeping files at a relatively low compression setting (I keep mine at 10) offers high quality and fast upload speeds.
This is not a file format offset printers like to print from so if you are having your images offset printed they need to be saved as either tiff or eps files. (And don’t forget about CMYK color mode.) If printing to a laser or ink jet printer, this format works just fine.
PNG – stands for: Portable Network Graphics.
GIF – stands for: Graphics Interchange Format.
Both these files are utilized primarily for web and computer screen viewing purposes. Up until a few years ago gif was the primary format for saving flat color images. It is being used less today and being replaced by the png format mostly because gif does some compressing (which translates to lower quality) and can’t handle the depth of colors that png can. (16 million for png vs 256 for gif.) PNG files also do a nice job of feathering edges for transparent background use.
Besides it’s use when a transparent background is necessary, a png file should be used instead of a jpg file for text-as-art images on the web. For instance if you’re using art as part of your navigation. The same is true if you’re displaying any art that is made of solid colors – unlike a photograph that is a mix of colors and shades. You’ll find that the edges of your words and images are much sharper using a png format.
EPS – stands for: Encapsulated PostScript.
EPS was developed by Adobe and is a standard file format for importing and exporting PostScript files and usually contains a thumbnail image associated with it. An eps file can contain any combination of text, graphics and images. Typically you’ll save drawing program files – Adobe Illustrator for example – in this format. Many vendors still like this format for outputing logos and other line art but by-in-large this versitle format is being replaced with the pdf format.
TIFF – stands for: Tag Image File Format.
Developed by Aldus in the early computer days this format is primarily used for offset printing. It’s not a file widely supported in the web world. I save all my images for offset printing using this format. The option exists to compress the file while saving, and years ago when disk space was an issue I used to do that, but not any more. Besides, not all printers liked a compressed tiff file.
These are just a few – but most popular – of the many digital formats available to you out there. Hopefully some of this has helped. Look for more on printing and resolution issues in other articles.