Frequently Asked Questions

Understanding File Formats

All graphic image file formats fall into two categories, either Bitmap formats or Vector formats.

Vector formats use mathematical formulas to recreate graphics. If the graphic is a circle, the file format will have the location of the circle's center, it's radius and other pertinent information such as what color to draw the circle. Vector formats are easily scalable without creating jagged edges, but they are only suitable for simple drawings with a few colors. Scanners do not use vector file formats.

Bitmap formats store the actual color of each dot in the image. They are more suitable for scanned images due to the large number of colors and complex tonal variations in a photograph. A disadvantage to Bitmap formats is that they create large files that take lots of drive space to store. This problem is over come by several bitmap file formats which compress the data prior to storage on disk.

Most scanning programs, including iPhoto Plus and Picture Publisher, use the *.TIF file format as their default. *.TIF files use compression but it does not shrink the file sizes significantly unless the image is black and white (Scanned in Line Art Mode).

Another popular file format is the *.BMP file. This is the format Microsoft uses for Windows Wallpaper. So if you want to use your own photos as Wallpaper, save them in the Windows directory in the *.BMP format.

The two most popular bitmap file formats today are *.GIF and *.JPG. Both of these formats are popular on the Internet because of their high compression ratios.

*.GIF compression uses an algorithm similar to ZIP files. It also reduces the number of colors in the image. A scanned image can have up to 16.7 million colors. A *.GIF file reduces this down to a maximum of 256 colors. With appropriate utilities, you can reduce this even further to 16 colors. Obviously you wouldn't want to do that with a photograph though.

*.JPG does not reduce color depth. It merely uses compression algorithms similar to ZIP files. This is the most popular format for scanned images on the Internet and for sending pictures as attachments to e-mail.

For more help with scanning graphics for the Internet, see our Internet Graphics Tutorial.