Resolution is the number of dots or pixels that make-up your photo. We need at least 100 DPI per inch of the puzzle that you are ordering. If your photo contains too few pixels, it is considered low resolution. When your image is uploaded at PortraitPuzzles.com, our servers measure the number of pixels, and will let you know if you can continue ordering with that image. We do not accept low resolution images, as the print quality would be unacceptable to us.