Digital Printing 101
If you have ever given your printer, graphic designer, or project manager a difficult time over image quality, this blog post is for you! Digital printing uses digital techniques developed for computer printers such as inkjet or laser printers. The ink or toner does not permeate the substrate, but forms a thin layer on the printing surface and may, in some systems, be additionally adhered to the substrate by using a fuser fluid with heat process (toner) or UV curing process (ink). 
Business cards, posters, invitations, banners, letterheads, pamphlets, and postcards are some items that are commonly digitally printed. When developing designs that will be digitally printed, the graphics files should be created in a vector (outlines) or raster (bitmap) based program such as Adobe Illustrator, Adobe Photoshop, or Adobe InDesign.
Not sure about the difference between vector and raster files?
- Vector files contain images created with outlines or line segments and curves. The most common formats for vector files are EPS (Encapsulated Postscript), AI (Adobe Illustrator), or PDF (Acrobat). A good example of something that would be saved as a vector file is a font.
- A raster image (bitmap) is made up of tiny dots, and each dot can be one of many thousands, if not millions of colors. There are also two color modes or pallets – CYMK (Cyan, Magenta, Yellow, and Black) and RGB (Red, Green, Blue). Generally, the RGB color space is larger and produces the most vibrant colors. Common raster file formats include TIF (or TIFF – Tagged Image File Format), JPG (or JPEG – Joint Photographic Experts Group), and GIF (Graphics Interchange Format). A good example of something that would use a raster format is a photograph.
The biggest difference between Raster and Vector file formats is that a vector image can be infinitely enlarged without distortion, whereas the amount a Raster (bitmap) image can be increased depends upon the original resolution, and accepted loss of clarity versus the accepted viewing distance. It is usually recommended that you keep the final output resolution between 100 and 200 DPI (dots per inch) at FULL SIZE. Go below 100 DPI and you will start to sacrifice quality - go over 200 DPI, you will greatly increase processing time. Although input files are usually 100-200 DPI, many printers typically print at between 360 and 720 DPI. This ensures the smallest droplet and lack of graininess.
In general, when dealing with digital image files, there are a couple of things you should keep in mind:
- Be careful of GIF files, as these are most commonly used for websites and are often not of a high enough resolution to be significantly enlarged.
- While EPS, PS, and AI files commonly contain vector data, they can also include bitmap data as well.
- TIF’s, JPG’s and GIF’s only carry raster data and do not carry any vector data.
- JPG files use a compression scheme to reduce file size (TIF’s may or may not use an optional file compression) – if you continually re-save a JPG file, it is continually compressing it. This can also lead to reduced quality.
Don’t worry! This post doesn’t end with a quiz, but I hope you take away a general understanding of why we can’t print the image or logo you copied and pasted from a website!