DPI is an abbreviation for Dots Per Inch, and specifies the number of dots in a square inch that make up an image on a printed page. More dots in a square inch mean a smoother image, whereas an image with a low DPI, the dots may be visible to the naked eye.
Since deviantART Prints automatically scales the source file to fit the entire print, we ignore the DPI information saved in print source files
. The number that matters the most is the DPI (or PPI = pixels per inch) of your image when it is printed on the largest sized print that you want.
You can find out the DPI of your image when it is on a print by dividing the largest dimension of the image by the largest dimension of the print.
For example, if your image is 3000x4500 and you wanted to make a 20x30 print available, your DPI is 150 because 4500 divided by 30 = 150. The minimum acceptable DPI for a deviantART Prints is 100 DPI, although images at this resolution are heavily scrutinzed for any defects or pixelization, and will be rejected if any is found. The recommended minimum DPI is 150, while 300 DPI will make an excellent quality print.
The DPI (or resolution) setting in Photoshop and other graphic programs is ignored by deviantART Prints, so it doesn't matter what you set it to. Effectively, only the image dimensions in pixels determine the resolution of your print file. However, you can set it to the DPI of the largest sized print so that when you work in actual size, you have an idea of how detailed it is going to be when it is printed (note: this only applies when you are creating a new digital image, and digital photographs already contain a set dpi when the picture is taken, raising the quality settings on the camera will give you a higher dpi)
. Below is an example of what the dialog looks like in Photoshop: