Pixels vs Points
Many people still believe that point values equate to pixels, which is not entirely true. The two units were equal back when the first iPhone was released in 2007: 1pt was equal to 1px. However, with the appearance of retina displays, 1pt became equal to 2px. Therefore, it is better to think of pixels as the real values based on the density (@2x - iPhone 4, 5 and 6 and @3x -iPhone 6 Plus), while points as the values for the first generation of iPhones. Quick respond to evolving requirements throughout the development and increased adaptability of the project to the changing business goals; A lightweight framework for developers - more productive time to build software;
San Francisco Fonts
Since the release of OS X El Capitan and iOS 9, San Francisco has been the default font made by Apple Inc for its products. The introduction of the new fonts has affected the design for the iOS operating system. The tracking value and text/display settings are adjusted automatically in accordance with the font size. This ensures the readability of the typeface. If the font is 20 pt or more, use San Francisco UI Display, in other cases choose SF UI Text. Although, you can only apply these tracking values in Photoshop, there is a formula of how they can be converted into Sketch: font size * tracking / 1000. There are different plugins for Sketch that can help you quickly calculate the proper character spacing values.
There are four main resolutions of iPhones: 320 x 480 pt for iPhone 4, 320 x 568 pt for iPhone 5, 375 x 667 pt for iPhone 6 and 7, and 414 x 736 pt for iPhone 6 Plus and 7 Plus. On the basis of the screen resolution, the layout expands rather than scales. iPhone 6 Plus and iPhone 7Plus are the only devices in the iPhone line that act similar to iPads when in landscape mode. As we have already mentioned, the tab bar is replaced by the left navigation menu on these smartphones.
There are two main resolutions of iPads: 768 x 1024 pt for iPad and 1024 x 1366 pt for iPad Pro.The two new features has been introduced to iPad with the release of the iOS 9: Split View and Slide-over:
- Slide-over is a small panel that appears on the right side of the screen when you slide the screen to the left when inside the app;
- Split View is a multitask feature that allows users to run two applications simultaneously in a portrait mode
App icon is essential when it comes to your application’s branding. The icon is the first thing that users see when they have their first experience with it. The icon is how your app is presented in App Store, on the home screen of the user’s device, in Spotlight and Settings. The app icon in the iOS 9 has its specific template. THere is no need to generate @1x assets, as they are no longer supported for the Apple’s smartphones. So today the two main resolutions are @2x and @3x.
Each icon has its three version - a basic version, and version of Spotlight and Settings. @1x and @2x are the two resolutions used on iPads
Shape and Grid
Starting from iOS 7, Apple has been using superellipse-shaped icons instead of the simple icons with rounded corners that had been used before. Nevertheless, keep in mind that you should not submit to App Store the icons with the mask if you do not want to find black artifacts. Simple square assets will do perfectly well. When designing iPhone apps and some of the icons, Apple used a golden ratio. This means that the icons keep perfect proportions. You can follow the Apple’s example, but it is not obligatory. Even Apple’s designers often depart from this rule on many icons.