Image Size and Resolution for Printing

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Your image's resolution is measured in Pixels per Inch (PPI). You can determine the size of your printed image by dividing the number of pixels by the pixels per inch. The higher the image's resolution, the smaller the image is when printed. So, for example, an image that is 200 pixels high and 400 pixels wide and that has a resolution of 100 PPI prints at 2 inches high and 4 inches wide. An image with the same dimensions but a resolution of 200 PPI prints at 1 inch high and 2 inches wide.

Inkjet and laser printers print images by applying dots of ink on paper. A printer's resolution is therefore measured in Dots per Inch (DPI). It takes more than a single dot to produce a particular printed color , so DPI is not equivalent to PPI. You can see, then, that the appropriate image resolution for a printer is not the printer's resolution. Table D.1 displays a few recommended image resolution ranges for particular printer resolutions .

You can alter an image's resolution with I mage > Resi z e. As Figure D.1 shows, the Print Size panel of the Resize dialog box has controls for Resolution . First, be sure that the check box located near the bottom of the dialog box and labeled Resample using is unchecked. Then choose the units (usually Pixels / Inch in the United States) and set the amount. The Width and Height will automatically be updated. As you'll see shortly, though, you don't need to use Resize in order to print your image at the proper size or resolution, because you can alter the image's resolution temporarily by letting your printer scale the image.

Figure D.1. Set the image's size and resolution using the Resize dialog box.

Table TABLE D.1. IMAGE RESOLUTIONS FOR PRINTING

Printer Resolution	Image Resolution
300 DPI	72 to 120 PPI
600 DPI	125 to 170 PPI
1200 DPI	150 to 200 PPI

NOTE

CAUTION

If Resample using is unchecked, the data in your image is not changed, and its quality will remain unchanged.

However, if Resample using is checked, adjusting Resolution or Height or Width changes the data in your image. The image will be stretched or shrunken. Because this stretching or shrinking adds or subtracts pixels, the quality of your image could be adversely affected.

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