Formats and resolutions for images
Understanding the difference between various art file formats can be daunting, but we hope this article will help explain the differences, and help you understand the best art file format to use for your specific need.
In this article
Art Files and Resolutions
There are two major types of image files:
Bitmap files are pixel-based images, and include those with
.gif extensions. All three types are made up of a number of pixels (tiny squares in a rectangular grid) in black, white or a variety of colors. Imagine a piece of graph paper with certain squares filled in with various colors to create a picture.
At normal size the squares are unnoticeable, forming a smooth-looking picture. When a bitmap is enlarged, so are the pixels. Because the squares are more noticeable, curves and angled lines take on a "stairstep" look. This jagged characteristic means that if you enlarge a bitmap image, it won’t look as good as when displayed at its original size or when reduced in size.
The way bitmaps build images lends itself to photographs and detailed illustrations that have significant shading or texture.
Below is a list of the formats we provide and their resolutions in pixels per inch (ppi):
- Color JPEG (.jpg) - either 150 ppi, 300 ppi or 600 ppi, depending on the image
- B&W TIFF (.tif) - either 300 ppi or 600 ppi, depending on the image
- Grayscale JPEG (.jpg) - 300 ppi
- Color WMF & (EPS - Mac) - varies per image
- B&W WMF & (EPS - Mac) - varies per image
TIFF (.tif) is a widely used standard for BW and color art. However, sometimes a TIFF’s file size is huge, which slows printing and gobbles disk space. In those cases, we offer the image as a JPEG, which renders the same-sized art in a smaller file.
JPEG (.jpg) files compress the file’s information, which makes the file size smaller. JPEGs are used primarily for photographs or artwork that has a lot of shading or gradations. JPEGs can be displayed on the Web.
TIF and JPG files are usually recognizable by both Windows and Mac-based operating systems.
GIF files are intended only for use on websites or for screen display. Because our GIFs have a low resolution (72 ppi, the resolution of computer monitors), they're not meant to be printed. We include GIFs so you can put them on your Web site. The images you see on our website are GIFs.
Vector artwork ends with extensions such as WMF, EPS and AI. Vector images are made up of objects or groups of objects. These shapes are formed by a series of points connected by straight or curved lines. Vector file sizes are typically smaller than bitmaps. The curves and angled lines of a vector are much sharper and don’t create the "stairstep" look of a bitmap, making them much better for enlargement.
With any resizing, vector images retain their clarity and detail. By contrast, other images (such as JPG) often look stairstepped, ragged or blurry when enlarged. So when you're enlarging a picture for banners, posters and other large items, use a vector file if one's available.
We try to include every image in WMF format, but some art styles and designs just don’t work as WMFs. Complex, detailed, stippled and crosshatched illustrations, continuous-tone photos, and textured images are often troublesome as WMFs. WMF files are recognized usually only by Windows systems and EPS only by Mac computers.