Designing for Retina display
Building apps for the iPhone 4’s Retina display involves creating two sets of images—one at 163ppi and another at 326ppi. After slugging our way through an app build or two, we feel confident that we have a decent workflow for attacking future Retina display app designs. Hopefully this information is of use to other designers.
When it comes to building UI elements that scale easily in Photoshop, bitmaps are your enemy, because they pixelate or become blurry when scaled. The solution is to create solid color, pattern or gradient layers with vector masks (just make sure you have snap to pixel turned on, where possible). While a little awkward at times, switching to all vectors does have significant advantages.
