The following are terms pertaining to resolution. I've included other
terms here for clarity. Pardon me if you already know the following:
SPI (samples per inch) is scanner and digital image resolution. To
scan an image the scanner takes a sampling of portions of the image.
The more samples it takes per inch, the closer the scan is to the
original image. The higher the resolution, the higher the SPI.
PPI (pixels per inch) is the number of pixels displayed in an image. A
digital image is composed of samples that your screen displays in
pixels. The PPI is the display resolution not the image resolution.
(Adobe Photoshop uses PPI and Corel Photo-Paint for example uses DPI
for image resolution so it's no wonder most users are confused.)
DPI (dots per inch) is a measure of the resolution of a printer. It
properly refers to the dots of ink or toner used by an imagesetter,
laser printer, or other printing device to print your text and
graphics. In general, the more dots, the better and sharper the image.
DPI is printer resolution.
LPI (lines per inch) refers to the way printers reproduce images,
simulating continuous tone images by printing lines of halftone spots.
The number of lines per inch is the LPI, sometimes also called line
frequency. You can think of LPI as the halftone resolution.
(Excerpted from "Desktop Publishing - Resolution Inch by Inch" by
Jacci Howard Bear, About.com, copyright 2003)
"Resolution Inch by Inch - Part 1: samples, pixels, dots and lines per
As the comment below implies, 300 DPI and 300 PPI are interchangeable
terms and are basically the same.
Personal knowledge - I've answered a similar question before about to
I hope this helps you. Should you have any comments/questions, please
feel free to post your clarification before rating this and I'll
attend to you as soon as possible. Thanks for asking.