DPI in photos vs DPI in Printers/Scanners [duplicate]

Question

When I look at the properties of a JPEG shot on my Canon 5D MkIII (set to the highest quality settings on the camera), i've noticed that the 'Horizontal/Vertical Resolution is 72 DPI'

My only previous knowledge of DPI comes from printers/scanners where standard scanners/print are set at approx 300 DPI for general day-to-day things and super high quality scans or prints are done in 600 DPI.

Since i have 22MP worth of image to use, i'm a bit confused as to what the image DPI means and how it relates to printing DPI (If it does at all). Can anyone clarify what Horizontal and Vertical DPI resolution means?

Answer 1

It really doesn't make a lot of difference in today's environment. At one time the dpi embedded in a picture's metadata, combined with the resolution of the image, told the printer what size the print should be. That is not so much the case any more as the software used to control the printer usually starts with a selected print size and scales the image to fit. To optimize printing you should match the resolution of your image to the printer's optimal pitch.

The origin of the 72 dpi (more accurately described as ppi) comes from the standard for displaying images on a computer monitor adopted early on by Apple. Microsoft/Windows, on the other hand, has defaulted at 96 ppi since the 1980s.

The 5760X3840 resolution of your 5DIII at 72 ppi would result in a print 6'8" by 4'5"!

For a very in-depth look at how dpi and ppi are related and involved in the printing process, see How do I generate high quality prints with an ink jet printer?