The terms Dots Per Inch (DPI) and Pixels Per Inch (PPI) are commonly used interchangeably to describe the resolution of an image. However, the terms do not mean the same thing and there are distinct differences between the two:
- DPI refers to the number of printed dots contained within one inch of an image printed by a printer.
- PPI refers to the number of pixels contained within one inch of an image displayed on a computer monitor.
Much of the confusion between these two terms happens for a couple of reasons. First, even though PPI refers to the resolution of an on-screen digital image, it can also affect the quality of the final printed picture. Second, even some professional print services request that pictures must be at a certain DPI level before they can be printed; what they normally mean is PPI, not DPI - thus, this adds to the confusion.
The term DPI is a method to determine the print size of an image on paper. Although some printing applications still use DPI, many newer printing applications instead have a setting so you can select at exactly what size (5x7, 11x17, or other) you want to print a photo. For printing applications that use DPI to determine the print size, increasing the DPI will make the size of the printed image smaller, while decreasing the DPI will make the size of the printed image larger.
PPI represents the quality of a digital image displayed on-screen. But, it also contributes to the quality of an image. If a digital image contains too few pixels, the picture will not have very much detail and appear pixelated. Digital images with more pixels have better detail. The amount of PPI is determined by the image size of the photo.
- Many digital cameras will have an image size setting in the camera menu. For the best picture quality, use the highest image size setting available on the camera when taking pictures.
- Refer to the operating instructions provided with your camera for information about possible image size settings.