PPI? DPI? What should I say?

Jul 26, 2010

I admit it—it’s confusing as hell! DPIPPI… A quick look over on Google clears things up. DPI is the acronym for Degreasing, Pickling and Inhibiting.

No, looks like that’s for the Hydraulicsdpi_ppi3sm.jpg Systems Maintenance crowd. For graphics folks, it means Dots-Per-Inch. Usually, this refers to the resolution of a printer or printing press, describing how many dots it can put down in a given distance.

Now, PPI, that’s Pixels-Per-Inch. We all know what pixels are, those flat little squares of image detail that start to look more like continuous tone the more densely you use them. They don’t really have any size. The resolution could refer to how many of these you pack into an inch or some other distance measurement.

dpi_ppi3.jpgI’m of the group that likes to stick with saying PPI for describing digital image resolution and DPI for printing hardware. For printed halftones, it’s best to use LPI, Lines-Per-Inch referring to the number of lines or rows of halftone dots going on the printed sheet, whereas DPI is best used to describe the resolution of a printer, in other words, how many dots it can image in an inch. They could be dots of ink, toner, or even exposure points by a laser to drum, plate or film (where it takes many of them to create an actual halftone dot or character of text). Little dots!

It’s even more confusing when you see DPI used in place of PPI all over the internet, even at some of the biggest outfits. But maybe they got where they are by making clients feel comfortable and speaking their language. I’ll guess they’ve probably adapted themselves to think: DPI=Details-Per-Inch.

Much more could really be said here; lots of ifs, ands and buts. But no.