# About image size and resolution

The image size (or pixel dimensions) of an image is a measure of the number of pixels along an image’s width and height. For example, your digital camera may take a photo that is 3000 pixels wide and 2000 pixels high. These two measurements have a direct correlation to the image’s file size, and both are an indication of the amount of image data in a photo.

Resolution is the fineness of detail you can see in an image. It is measured in pixels per inch (ppi). The more pixels per inch, the greater the resolution. Generally, the higher the resolution of your image, the better the printed image quality.

Although a digital image contains a specific amount of image data, it doesn’t have a specific physical output size or resolution. As you change the resolution of a file, its physical dimensions change, and as you change the width or height of an image, its resolution changes.

You can see the relationship between image size and resolution in the image size dialog box (choose Image > Resize > Image Size). Deselect Resample Image, because you don’t want to change the amount of image data in your photo. Then change the width, height, or resolution. As you change one value, the other two values change accordingly.

The same image printed at 72 ppi and 300 ppi; inset zoom at 200%

If you need to print at a specific resolution, or if you want to print an image significantly smaller or larger than the image’s pixel dimensions allow, you can resample the image. Resampling involves either removing or adding pixels to the image to achieve the desired dimensions or resolution.

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