Adobe Photoshop CS3 - Manual (Page 68)

PHOTOSHOP CS3
User Guide
61
Image size and resolution
About pixel dimensions and resolution
The pixel dimensions (image size or height and width) of a bitmap image is a measure of the number of pixels along
an image’s width and height. Resolution is the fineness of detail in a bitmap image and is measured in pixels per inch
(ppi). The more pixels per inch, the greater the resolution. Generally, an image with a higher resolution produces a
better printed image quality.
Same image at 72-ppi and 300-ppi; inset zoom 200%
The combination of pixel dimension and resolution determine the amount of image data. Unless an image is
resampled, the amount of image data remains the same as you change either the pixel dimension or resolution. If you
change the resolution of a file, its width and height change accordingly to maintain the same amount of image data.
And, vice versa. For more information, see “Resampling” on page 64.
In Photoshop, you can see the relationship between image size and resolution in the Image Size dialog box (choose
Image > Image Size). Deselect Resample Image, because you don’t want to change the amount of image data in your
photo. Then change the width or the height or the resolution. As you change one value, the other two values change
accordingly.