In the previous article, I explained some of the basics of image size, resolution, and file type. In this article I will get into a little more depth on additional file types and raster images vs. vector images.
Raster/Bitmap
As explained in the previous installment, a raster or bitmap image is one made up of a grid of pixels – tiny squares of color information that build the image. This type of image file can be large (in terms of KB or MB needed to store the file) depending on the image resolution and compression type. A raster image is also limited by the number of pixels contained in the image, in terms of how large it can be “blown up” or printed.
Vector and EPS
A vector image, the kind created by programs such as Adobe Illustrator, is created with mathematically determined paths that connect specific points in the image. These paths will stay clean and crisp no matter how large or small the image is scaled. Because they are not built of individual pixels, vector images typically have a smaller file size than raster images of comparable dimensions. Typefaces typically consist of vectors, allowing them to be scaled to accommodate different sizes.
Vector files created in various design programs can be saved as .eps files (encapsulated post script) which saves any font, color, or other information along with the paths that make up the image. However, just because a file is saved as an .eps document does not mean that it is a vector-based image. For example, photoshop files or other raster images placed in Illustrator will remain raster images, at their original resolution, regardless of the output file type. This format is ideal for placing graphics into other layout programs because it contains information that the native file format may lose outside of the program it was created in.
What is a pdf?
PDF stands for “Portable Document Format.” A pdf is not inherently either vector or raster; pdf is simply a way to save any file in a cross-platform format that anyone can view on any computer. Type and color information is preserved, regardless of what is installed on the recipient’s machine. The settings with which a pdf file are saved determine whether or not the file will be editable with programs such as Photoshop or Illustrator.
Some Notes on Color
Color is a complex art/science. Why do colors appear different on-screen than they do when printed? Why can colors vary so much from computer to computer? Individual monitor calibrations, printer types, and many other factors can alter the way colors look and can cause a lot of headaches between what a designer intends and what a client sees on the other end, especially with electronic proofing. By being aware of color modes and PMS standards, some of the guesswork can be taken out of this process. The two most common color spaces for design work are CMYK and RGB.
CMYK refers to the four colors used in process printing. C (cyan), M (magenta), Y (yellow), and K (black) are the four ink colors used in traditional press printing (and now, digital press printing) to create full color work. Ensuring that files are set up in CMYK colorspace will help ensure accurate printing results.
For images that are meant to be viewed on screen (such as web graphics), RGB color space is the standard. R (red), G (green), and B (blue) are the three colors of light produced by monitors to reproduce the visual spectrum electronically.
PMS (the Pantone Matching System) is a system used by printers to create specific ink formulas for color matching. PMS swatches are available in most design software programs and can ensure accurate reproduction of color for things such as logos. However, with so many print pieces being reproduced digitally now, PMS ink colors often have to be simulated with CMYK process colors, which can vary not only from printer to printer but also from print run to print run.
Your designer and printer are not speaking a foreign language, just using a specialized set of terminology to help ensure the best quality, most consistent results in handling your images, logo, and other design files through the design, print, and publishing process.







