My images in iphoto '11 are not sharp unless I zoom in

Before upgrading to iPhoto '11 from '09 my images looked good, but now they appear soft until I zoom in. The whole point of digital photography is to view your images in there best possible way. How can I get the images to look better when viewing in iPhoto? I'm using a Macbook 13" late '09. I hope I don't find I now need the new Retina display to view my images, when they were fine before the "upgrade"