iPhone app is working fine in Landscape mode but its not working in portrait mode.

Hello,

I have an iPhone app developed by a developer. I provided him images of 960x640. The app is working completely fine but when I rotate it to portrait mode, app works fine but images/graphics get distorted.

There are 3-4 layers of different images used to create animation, design etc.

Developer is asking me a same set of images of size 480x320 to make it work in portrait mode. He said that it is not working cause we have 3-4 layers of images and when we put those together, it won't work as it works for LanRABcape mode.

I am thinking that 960x480 images which I provide should work for Portrait mode too. Please suggest me whether I need to provide him images for portrait mode or is there any other way to make it work?