DPI is an acronym for dots per inch and is used to describe the resolution of a printed image. Inkjet printers work by dispensing ink across the page via a pattern of tiny dots. DPI isn’t a major factor in printer selection if documents are the only things being printed; however, if graphic charts or photos are to be printed, DPI is important.
When searching for a new printer for the home or office, people tend to look at the number of pages per minute, or ppm, a printer is capable of producing. If the main use for the printer will be document printing and a handful of charts or basic graphics, it’s unlikely that DPI is of any concern. However, if sharp, clear images or photo printing is desired, it’s necessary to check the maximum DPI of the printer. DPI printer resolution is denoted in one of two ways. You may see it as 'some number x some number DPI,’ or you might see it as 'some number DPI.’
To understand the concept of DPI resolution, consider a photograph that has been enlarged on a computer. As the photo expands, the image becomes blurry or fuzzy. The edges of people or items become less smooth, and pixels may be apparent. This is because the pixel density wasn’t adjusted, but the overall size of the photo was adjusted. When pixel density, or pixels per inch, isn’t adjusted for a photo re-size, the quality of the photo’s appearance will begin to suffer. What does this have to do with DPI? It’s simple: if you have a printer with a low DPI resolution and you try to print a very intricate photograph, the picture will come out on paper the same way the enlarged image on the screen appeared. Edges will be rough, color gradients will be poorly transitioned and the photo’s features may appear grainy or block-y. Remember that PPI is different from DPI; PPI refers to on-screen pixels that directly touch one another, while DPI refers to printed dots with in-between spaces.
Many standard photo-capable printers today offer the user the option of DPI adjustment. During print setup, there are usually drop-down menus for quality. Users can opt to keep the setting at ‘normal’ for standard printing, or select ‘maximum DPI’ when trying to print out a photo. Maximum DPI settings are best when used in conjunction with photo paper; if regular printer paper is used, the paper may be saturated when it leaves the printing head compartment. Understand, however, that your printer is not magically gaining a higher resolution; you are simply setting it to its maximum potential. Many people prefer to keep the DPI lower for basic documents because it uses less ink. For example, if you are shopping for a photo-quality printer and come across two separate printers, one that says 300x300 DPI and another that simply says 4800 DPI, select the 4800 DPI model. However, if you will be printing mostly word-based documents and few if any photos, opt for the 300x300 model. Your photos will not be crystal clear perfect, but you will probably save a few bucks.