Why is it that a picture that looks nice on your computer screen doesn’t look as nice when you print it? This degradation will happen if the resolution of the picture is lower than the size you want to print. Here are some tips to help prevent these kinds of printing disappointments.
Before you print a picture, check out its original size. To do this save your picture to the computer, right click on it, then click on “Properties” if using a PC or “Get Info” if on a Mac. See the pictures below:
For PC users, click on the “Details” tab and scroll down to “Image”. For Mac users, click on the “More Info” arrow. See below:
In both cases, the Width and Height of the image displays. In the examples above, the PC image (left) is 480 pixels for width and 359 for height — or 480 x 359. The Mac example shows 1243 x 902.
Two variables for printing are image Pixel size and the Dots Per Inch (DPI) of the printer which for most printers is 300. Using the formula:
Pixel Width / DPI
Pixel Height / DPI
yields the maximum width and height of your image (in inches). For example, if you want to print a poster-sized image with 18″ x 24″ dimensions, the formula says that your image needs to be 5400 pixels x 7200 pixels — a rather high resolution. It is acceptable to scale down an image but scaling up will result in a distorted, pixelated print. In short, always use higher resolution images when printing.