Scaling by a fixed value isn’t a good idea… as I’m sure anyone who used the accepted answer here probably found out when the iPhone 5 came out.
Here’s a code snippet to scale dynamically based on the screen resolution to eliminate the letter boxing.
// Device's screen size (ignoring rotation intentionally):
CGSize screenSize = [[UIScreen mainScreen] bounds].size;
// iOS is going to calculate a size which constrains the 4:3 aspect ratio
// to the screen size. We're basically mimicking that here to determine
// what size the system will likely display the image at on screen.
// NOTE: screenSize.width may seem odd in this calculation - but, remember,
// the devices only take 4:3 images when they are oriented *sideways*.
float cameraAspectRatio = 4.0 / 3.0;
float imageWidth = floorf(screenSize.width * cameraAspectRatio);
float scale = ceilf((screenSize.height / imageWidth) * 10.0) / 10.0;
self.ipc.cameraViewTransform = CGAffineTransformMakeScale(scale, scale);