That's correct. Retina graphics twice the resolution of non-retina. The easiest way to support both retina and non-retina displays is to make two copies of each graphic you use. Use the format imagename.png for the non-retina and imagename@2x.png for the retina image. When you want to load the image you can use this line:
UIImage* image = [UIImage imageNamed:@"imagename"];
iOS will automatically select the correct image.