Desiging Images for the iPhone and iPad
Cramming a high-resolution image that can be blown up to poster size onto an iPhone screen makes no sense. Not only would the photos not display correctly, but downloading a file that large would also take an inordinately long time and your visitors would likely abandon your site. Rather than force visitors to download large images on the home page of your mobile site, which iPhone users would access, you should ensure that your designs honor the constraints under which your users labor.
Sizing up image-sizing strategies
If you plan to put images on your mobile website, the design process goes more smoothly if you have a strategy to handle the different screen sizes, resolutions, and aspect ratios.
Sizing one image to fit both screens: A practical and timesaving way to create images optimized to work on both the iPhone and iPad is to create one web-optimized image that looks good on both devices. It isn’t a perfect science, but both the iPad and iPhone 4 have such great-looking displays that you can scale an image up or down quite a bit and it can still look quite good. Although this method isn’t foolproof, creating one optimized image is the simplest option, and it will work for many sites.
Using multiple image sizes: If you have the resources ...