DPI is an acronym for dots per inch and PPI stands of pixels per inch. The two concepts are not interchangeable and hence should not confuse anyone. However, since the two terms are used in a random way without really illustrating the technical differences, many people have started using both as interrelated terms. DPI is an older term. It is more applicable for printers. PPI is a more recent term and is apt for digital images, either those being captured by digital cameras or when images are being displayed on computers, mobile devices and being printed digitally.
Difference Between DPI and PPI
Both DPI and PPI affect the resolution of the image in question. DPI or dots per inch does not affect an image. It is not a term used to define or depict the resolution of an image. It is almost always confined to the way a printer would print the colors or inks. In old CRT monitors, especially the early black and white ones, the resolution was often referred to in DPI terms. While that was not entirely wrong, it was still confusing.
For a printer, the number of dots in an inch the printer would create or put ink and colors in will determine its dots per inch. You can of course preset the printer to cater to a certain number of dots per inch. The more dots you have per inch, the better your image shall be. More dots per inch will lead the printer to use more ink per inch, the colors will blend seamlessly and you would get a higher quality image. The printing process or the speed will be slower if you opt for higher dots per inch. You would also use more ink. Smaller images being printed will require higher dots per inch as close inspection would make lower dots per inch look like a poor quality printout or even a pixelated image.
PPI is pixels per inch and it has a direct correlation with the size of an image. Have too few pixels per inch and the image will look distorted or jagged and may appear pixelated. Have enough or more pixels per inch and the image will be perfect for a given size. Smaller images that would be looked at from a very close distance will require a higher count of pixels per inch. Larger images that would be seen from a distance can do with more pixels per inch. As with DPI, having a higher PPI will cost more to print. But it will depend on the size of the image. You cannot use a very low count for a small image and you cannot use a very high count for a very large image.
