Which File Should I Use? 

First, a few definitions.

ppi =     Pixels per inch.  This refers to the size of the final printed image. An image that has a higher number of pixels per inch will show more detail than one which has fewer pixels per inch.

dpi =     Dots per inch. This is a measurement of the scanning resolution of an image or the quality of an output device. DPI expresses the number of dots a printer can print per inch, or that a monitor can display, both horizontally and vertically.  The more dots per inch, the sharper the image.

ppi versus dpi = It’s easy to understand, but takes a little lengthier explanation try these links or google dpi versus ppi

http://graphicdesign.about.com/library/weekly/aa070998.htm - has some good links!

JPEG = A standardized image compression mechanism. JPEG stands for Joint Photographic Experts Group, the original name of the committee that wrote the standard. A form of image compression that reduces the size of a graphic file by discarding some image data. JPEG compression can make a file very small, but it is "lossy," meaning that image quality is lost when the image is compressed. JPEG compression is generally suitable only for use on the World Wide Web; it is not generally considered appropriate for print images.

TIFF =   Tagged Image File Format. A graphics format which was originally created for scanned images. TIFF is widely used in the newspaper industry and for desktop publishing because of the very high quality and high resolution (lots of pixels). However, it is not very useful on the Internet for two reasons. 1.) TIFF files are very large, often requiring many megabytes, and therefore take a long time to send across a network (especially at slow modem speeds). 2.) TIFF files can not be compressed resulting in much larger files.

Now that you’re versed in the lingo, here are some guidelines to help get you started.

 1. Printed Documents  - Use 300 ppi TIFF files for black and white as well as color printing.  If you’re printing on a small office printer, you may need to resize, but it’s best to use the 300.

 2. Web or PowerPoint Presentations – Use 72 ppi JPEG file.  Your computer screen can only show 72, so using a 300 isn’t going to make any discernable difference in image quality.