On the iPhone 5S the image saved to the camera roll is only 4,2 MP (2048x2048) instead of 6,0 MP (2448x2448). It does not matter wether the image was posted on Instagram using the camera function in the app or if it was an image chosen from the camera roll. It down converts it nevertheless. The bug seems connected to the iPhone 5S, my previous iPhone 5 worked flawlessly with the same Instagram version as well as iOS version. I also tried on a friends iPhone 5S to make sure it wasn't a local problem. I have filed a bug report on Instagram (with no reply from them whatsoever), but wanted to check if anyone else is troubled by this and know a solution.