Improperly set resolution can lead to a host of problems, including banding, blurry or pixelated photos, or long wait times when printing. To add to the confusion, printer resolution and image resolution are two different things.
Printers measure resolution in dpi, the number of dots they lay down per square inch of paper. Depending on the printer, resolution can be as high as 4,800 by 2,400 dpi. (Printers reach these resolutions by layering dots on top of one another as they print.) Higher dpi settings mean longer print times and more ink used, but they may not translate into a higher-quality print. Most printers don’t let you set printer resolution directly, but selecting a higher print-quality setting probably means you’re printing at a higher resolution.
By contrast, image resolution is measured in ppi, or pixels per inch. If you have too few pixels per inch, your image will appear soft or the pixels themselves will become apparent—producing jagged lines and blocky details. But there’s no benefit to having too many pixels per inch; that can choke your printer and won’t give you a better print. The ideal image resolution varies from printer to printer, but the range is between 150 and 360 ppi. In Adobe Photoshop and Photoshop Elements, you adjust resolution from the Image: Image Size and Image: Resize menus, respectively.