Why do people think DPI is a measure of digital image resolution?
A. Mostly it’s the fault of software manufacturers who have labelled the DPI setting in their program under the title of “Resolution”. The DPI figure is used as a conversion factor by some software to either re-size the photo and/or set its ppi output to paper. These are legitimate (and can be very handy for people such as graphics designers), but with the logic of 2+2=5, people have erroneously concluded that because DPI can change the photo in these ways, that if the same photo had two different DPIs, the higher DPI photo would represent more “resolution.” In reality, if two digital photos have the same pixel dimensions, they are identical in digital resolution no matter what the DPI setting in the photo. DPI, unless used to re-sample (re-size) the photo, does not create “resolution” – but today many people will still think that if they have two photos of the same pixel dimensions, one set to 72 dpi and one set to 300 dpi, that the 300 dpi photo is “high res” and the 72 dpi photo is
