iMovie- Pictures become blurry after import

We are trying to make a slideshow of pictures in iMovie HD. We first put the photos into iPhoto, and the pictures looked great. Then, after importing them into iMovie HD, we noticed that the pictures looked blurry. We compared the pictures imported into iMovie to the pictures in iPhoto, and the ones in iPhoto had much better quality. We into the playback button in the preferences of iMovie HD to make sure that it was at the highest quality, and it was. We are very confused, and it will be greatly appreciated if someone can tell us the answer to our problem. Thanks! 🙂