Hey all. I am trying to make images for an iPhone app and the specs I'm reading say the screen is 320x480 with a ppi of 163. The iPhone 4 of course is double those numbers but for the sake of example I'll use the original specs. I'm not too familiar with how vector graphics work and I'm having trouble with this. If I make an image at 320x480 and export it from Illustrator at 163 ppi, the image output becomes 724x1087. If I export it at 72 ppi it will turn out with the proper starting resolution of 320x480. The images are all exported as .png files and they look more or less okay except I will get edges cut off of the right and/or bottom of a lot of the images. I have to make the artboards bigger than the images to compensate for the cutoff.
So basically there are two questions here: what's going on with the ppi and how to I keep the images from cutting the edges during export? Dunno if the two are related but the ones at a higher ppi seem to retain their edges while the lower ppi cuts them off.