[ Thanks to slonkak for this link.
]
“One of the most mundane tasks I have to perform after
a photo shoot is editing the dots per inch (DPI) of the
almost-finished photos so that they print at the correct sizes
(4×6, 5×7, etc.). This process usually involves me opening each
photo, one at a time, and increasing the DPI until I see the print
size reach the desired dimensions. For a couple photos, while
mundane, this task isn’t bothersome. However, when there are 96
photos to alter as in one of my recent shoots, this task can take
forever.“In a Charles Epps moment, I realized that math could solve this
problem. So the first thing I did was derive the equation I would
need to determine the needed DPI of a photo:”