What resolution to set for designing iphone apps in Photoshop?

Question

Taking iphone 3.5" retina as reference, I'm confusing with which resolution to set for designing in photoshop.

I've read some saying to design iphone apps in 640x960 326dpi here and some saying that dpi doesn't matter (in the comments below).

So, is there a difference between designing in 640x960 72dpi and 640x960 326dpi?

Answer 1

For layout purposes, dpi doesn't matter. Position something 10pts away from the edge and it will be about 10pts away from the edge regardless of dpi. When showing text and images, the OS will show at the best resolution it can.

That's why two forms of the image should be stored with the app. MyImage.png and MyImage@2x.png. The @2x image is just that, an image that is double in size that will be shown in the same position and size as the original, just at a better resolution.