Today’s Question: When I resize and resample to enlarge a print in Photoshop and want to check the pixels to see how the image might look printed I get confused. When I look at it “print size” it doesn’t appear nearly as large as the intended print. However if it looks good using this selection, does that mean it will look this good when printed? And what is 100 percent zoom for? I feel unsure how to use these two options.
Tim’s Quick Answer: The Print Size view option is intended to provide a sense of how large the current image will appear when printed, not for evaluating image quality. To evaluate sharpness and other details related to overall image quality, the 100% (“actual pixels”) view option is best, as it ensures that each pixel in the image is represented by a single pixel on your monitor display.
More Detail: It is important to keep in mind that the Print Size option will not produce an accurate indication of the actual print size for most users, based on the default settings in Photoshop. Fortunately, you can resolve this issue so the Print Size preview actually reflects the print size for the current image.
First, you need to determine the pixel per inch resolution of your display. First, determine the actual pixel dimensions of the display within the settings for your operating system. Then measure the actual width of the display. Divide the number of pixels across by the width of the display. For example, my MacBook Air is set to a resolution of 1440×800 pixels, and the width of the display is 11.25 inches. Therefore, the pixel per inch resolution for this display is 128 pixels per inch (ppi). Note that the resolution of most displays, contrary to popular belief, is not 72 (or 96) ppi.
To adjust the display resolution setting in Photoshop go to the Edit menu on Windows or the Photoshop menu on Macintosh, and then choose Preferences > Units & Rulers. In the New Document Preset Resolutions section at the top-right of the Preferences dialog enter the resolution value you calculated into the Screen Resolution field, making sure that the popup is set to the correct unit of measure. Click OK to close the Preferences dialog.
With the actual pixel per inch resolution for your display established in the Preferences dialog in Photoshop, when you set the view option to Print Size the image will appear at the actual size that it will be printed. Keep in mind, of course, that the print size is based on the current output resolution and dimensions for the photo, which can be found in the Image Size dialog (Image > Image Size from the menu).
As stated above, the Print Size view option should be used for getting a sense of the output size, not for evaluating image quality. Instead, evaluating for sharpness and other factors related to image quality should be done at a zoom setting of 100%. At a 100% zoom setting one pixel in the image is represented by a single pixel on the display, so you are getting an accurate view of the information contained within the photo.
You can switch to the 100% zoom setting by choosing View > 100% from the menu (this option was called “Actual Pixels” in earlier versions of Photoshop). You can also establish a 100% zoom setting by double-clicking on the button for the Zoom tool on the toolbox, or by pressing Ctrl+Alt+0 on Windows or Command+Option+0 on Macintosh. Note that the last character of this keyboard shortcut is the number zero, not the letter “O”.