I learned in a photography class years ago that photographed images are made up of tiny points of light called “circles of confusion.” In the digital age, these dots have become squares called pixels and a bunch of pixels make up an image. When an image is opened in Photoshop, it is “rasterized,” and those dots become squares. So dots per inch are actually squares, or pixels, per inch, thus the term “dpi.”
Your eye views an image on your computer at approximately 72 dpi. At this resolution, the image is quite clear. However, a 72 dpi image is low resolution and inadequate for print.
If your painting has been chosen to appear in a magazine, (and who doesn’t want this to happen) the magazine will request a 300 dpi copy of the image. This is considered a high resolution image suitable for print. High resolution images shouldn’t be used on a website or Facebook or Instagram, or anywhere you don’t want people to hijack your pictures. But you do need 300 dpi images if you want to have giclee prints made, or sent to a print magazine.
So the question is: I have finished a painting and photographed it. How do I change the resolution?