Originally Posted by SarahMB
I did not realize that we could specify different files for different situations and different types of readers.
Actually, you cannot. You cannot specify to use a specific image based on the screen size. You can't do "if it's an iPhone, use the smaller image and if it's an iPad, use the larger image" Standard ePub does not work like that. You have to build your ePub to fit most situations.
But what you can do is make your images aspect ration correct for most screens and then if you make them full screen, they will fit. Like the cover or maps.