Calculating the correct fi le resolution

Calculating the correct fi le resolution


Resolution for print If you shoot digital photos, your camera will preserve either all the pixels that are captured as raw fi les or a portion of the pixels that are captured as small, medium, or large JPEG fi les. If you use a scanner to acquire images, you can control the number of pixels the device captures by setting the input resolution in the scanner software.
High-resolution photos contain more pixels, and therefore fi ner details, than low-resolution photos, but they also have larger fi le sizes, take longer to render onscreen, require more processing time to edit, and are slower to print. Low-resolution images, however, look coarse and jagged and lack detailwhen printed. Your fi les should have the minimum resolution to obtain the desired output quality from your intended output device at the desired output size — but not much higher. Th ere are three ways to set the resolution value for your digital fi les.
➤ If you open raw digital or JPEG photos into the Camera Raw dialog, which we highly recommend, you can specify an image resolution there
➤ After opening your fi les into Photoshop, you can change the image resolution in the Image Size dialog
➤ When scanning photos, you’ll set the image resolution using the scanning software for that device.
Th e print resolution for digitized images (from a camera or scanner) is calculated in pixels per inch (ppi). A–C For output to an inkjet (desktop) printer, the fi le resolution should be between 240 and 300 ppi.
Commercial print shops have specifi c requirements for their particular output devices, so it’s important to ask them what resolution and halftone screen frequency settings they’re going to use before choosing a resolution for your fi les. For a grayscale image, the proper resolution will usually be around one-and-a-half times the halftone screen frequency (lines per inch) setting of the output device, or 200 ppi; for a color image, the resolution will be around twice the half tone screen frequency, or 250–350 ppi.