One of my first icon projects for Campaign Monitor was to create a set of Apple iOS icons for our mobile web application. These are the icons that show up when you bookmark our mobile site to the ‘home screen’ on your Apple device. Now, with all of the iOS devices floating around out there, you can do things the easy way by creating one large icon which is then scaled down for that particular device, or you can do it properly by creating a pixel-perfect icon for each device. For the iPod Touch/iPhone 2.5/3G/3GS, the icon size is a miserly 57 pixels square. For the iPad, it’s 72 pixels square, and for the newer iPhone4, it’s a whopping 114 pixels square.
The challenge with iOS icons, or for that matter, any icon that will be used at multiple sizes, is that you need to come up with an idea that is memorable and interesting, whilst keeping things clear and concise enough that it is still recognisable at smaller sizes.