Key Difference: Resolution is the term that is used to describe the crispness and detail of an image. DPI is a unit of measurement, which determines how many individual dots can fit into a 1x1 inch square.

Resolution and Dots Per Inch (DPI) are terms that are usually used when printing photos or referring to camera and printer settings. These two terms though used in similar contexts, differ from each other greatly. However, DPI does affect the resolution of an image. The higher the DPI and the resolution the better the image, but it will also be bulky and take up more space on the computer. Let’s differentiate both the terms.

Resolution is the term that is used to describe the crispness and detail of an image. While an image is magnified, they tend to blur and lose their detail qualities. Resolution is ability of an image to retain the image’s detail. Image with a higher resolution means more image detail, while lower resolution means less detail and more blurry image.

Resolution is defined by Dictionary.com as:

• The process or capability of making distinguishable the individual parts of an object, closely adjacent optical images, or sources of light
• A measure of the sharpness of an image or of the fineness with which a device (as a video display, printer, or scanner) can produce or record such an image usually expressed as the total number or density of pixels in the image <a resolution of 1200 dots per inch>
 
 
• In Physics & Chemistry: The act or process of separating or reducing something into its constituent parts: the prismatic resolution of sunlight into its spectral colors.
• The fineness of detail that can be distinguished in an image, as on a video display terminal.

Resolution of digital images can be described in many ways including pixel resolution, spatial resolution, spectral resolution, temporal resolution and radiometric resolution. Pixel resolution refers to the pixel count in a digital image. Spatial resolution is how closely lines can be resolved in an image. Spectral resolution is the ability to resolve features in the electromagnetic spectrum. Temporal resolution is the ability of movie cameras and high-speed camera to resolve events at different points in time. While normal movie cameras can resolve 24 to 48 frames per second, high speed camera may resolve 50 to 300 frames per second. Radiometric resolution determines how finely a system can represent or distinguish differences of intensity, and is usually expressed as a number of levels or a number of bits.

DPI or Dots per Inch is a unit of measurement, which determines how many individual dots can fit into a 1x1 inch square. These are used to measure the resolution of monitors, TV, when printing images using a printer. When describing the resolution of monitors and TVs, it is usually confused with pixels per inch (PPI), which is how many pixels can be fitted into an inch. Video displays are rated in a dot pitch, which refers to the space between sub-pixel red, green and blue dots of a pixel.

In terms of printing DPI is used to describe the resolution of dots per inch in a digital print or photo. This is most commonly related to the type of printer a person has. Depending on the printer, it can print images with different resolutions. For example, a dot matrix printer can print in the range of 60 to 90 DPI, while an inkjet printer is capable of printing 300-600 DPI and a laser printer can print 600-1,800 DPI.  Higher DPI of images results in a high resolution of the image, which produces a crisp and clean picture. In printing, DPI (dots per inch) refers to the output resolution of a printer, while PPI (pixels per inch) refers to the input resolution of a photograph or image. When printing an image, a person should ensure that the DPI is equal or higher than the PPI, in order to produce a sharp and clear image. Many printers also come with built-in default DPI settings in order to produce proper and clear images in every print.

Image Courtesy: help.adobe.com, forums.zenfolio.com