Button images for UIButton scaling on iPhone 4 much smaller then appearing on simulator or iphone 3

The images on a few UIButtons are getting scaled down way smaller on the iPhone 4 compared to how the show up on interface buil开发者_如何学Goder, the iPhone simulator or an iPhone 3G. How can I ensure the button images stay the same size as they appear in IB?

Do you have two images, e.g. one for 320*480 and one for 640*960 screen resolution? E.G one file named myImage.png and one named myImage@2x.png?