How do you get iMovie 11 to save imported photos at a higher resolution

When you import a picture into iMovie 11 from Aperture or iPhoto, iMovie creates an copy of the picture at a lower resolution and uses that picture in the video. It is often blurry and of worse quality than the original and looks bad in HD. Some of the copies (reveal in Finder) are only 200k.

You can fix this by dragging a higher quality photo from Finder on top of the same photo in iMovie and choose "replace". Thereafter iMovie looks to the photo you dragged in for the source of the image. I'm finding that the difference is often dramatic in terms of the finished video. It's hard to tell how iMovie is making its decisions because some of the pictures it creates are okay and can be close to 1mb in size. There's no indication of what it's going to do with a photo or why and no apparent way to configure it.

Does anyone know how to get iMovie to take pictures from Aperture and iPhoto and not degrade them? In other words, to control the quality (e.g. image size, compression, whatever the heck it's doing) of imported photos?

Thanks.