I just imported all my pictures from my what used to be manually managed photo folders. I am now going to let iPhoto manage it. But, When it imports a picture and rotates it to the correct perspective, it creates a modified file. Fair enough. But the file size changes. An original 8.1mpx picture taken portrait on my 350D is about 4.4MB - once imported into iPhoto, the modified file is about 3.3MB. Is iPhoto lowering the quality of my pictures?