You may wonder which format is the best image type for web, why there are so many image types, when one should be used over another and why would you need to know. Should you use a PDF, GIF, TIFF, JPEG? Can anyone use a PSD file? Let's take the mystery out of it and make these file types a little easier to understand.
Vector files are those created with lines in a graphic editing program such as Adobe Illustrator. A logo file should originate as a vector so that it can be scaled larger or smaller without any loss in resolution. Typical vector formats are saved as AI, EPS or PDF. Graphics industry professionals should be able to use these types of files and edit them.
Photographs can be saved as JPG, TIFF, or PSD files. JPG files are compressed into smaller file sizes. This makes them the preferred universal image format for web use. JPG images can be saved at any resolution, therefore used for web or print. TIFF files include no compression. Therefore, TIFF file sizes are going to be large. PSD files are native Adobe Photoshop files and may contain multiple layers for editing capability which increases the file size.
GIF images are ideal for animated graphics and for graphics with very little color. These files can be saved with very customizable settings, thus allowing for smaller file sizes and are therefore useful for the web.
PNGs are also ideal for web use as they can shrink to very small file sizes. The advantage of a PNG is its ability to retain transparency. When you want to retain quality of a detailed image and file size doesn't matter, you want to use a PNG.
PDF files are best for sending composite documents and graphics to print. Their file sizes can be adjusted according to resolution. They may contain fillable forms, or be downloadable documents that are universally accepted regardless of application, computer or operating system.
If you don't work with these types of files on a recurring basis, you may not remember any of these differences. If that's the case, you may want to grab my downloadable Guide to Image File Types.