Save JPEGs as PSDs to preserve quality (Photoshop CS/CS2/CS3/CS4)

If you start with a JPEG image, perhaps from a digital camera, and alter it, don't save it again as a JPEG; you'll lose image quality every time you re-save an image in JPEG format. Instead, save the altered image as a PSD file and make a JPEG copy if you need to post the image to the web, for example. In the meantime, you'll have a good copy of your altered image in PSD format for use in other applications, such as for printing photos or using them in a printed brochure.