Camera Viewport Rect Not Work in iPhone 5?

Hello,

According to this article, I want to lock the aspect ratio of my 2D game for different device by letterboxing. It worked in Unity dev environment and android device. However, when I deployed it to my iPhone5, it seems that it ignores the code and stretched. Don't know if it's the cause but I compiled it in xcode 5.1 and deployment target to 6.0. Any help would be appreciated.

Mad