Why is it impossible to export a file with the same fidelity as the version iMovie itself plays for me?

My movie is a photo slideshow using Ken Burns effect throughout, using iMovie 09. It looks beautiful when I play the project directly from within iMovie, even when enlarged to fullscreen playback. Is there really no way to set the quality settings high enough to reproduce this level of quality in an exported file? It seems so, and I don't understand why. "Export to iDVD" is a joke--even with the best quality settings there is an incredible amount of moire patterns and jagged edges. Exporting to Quicktime is better, but still the comparison with the version played from within the application is very poor. I wouldn't care if my computer had to crunch all night to render a file (and my movie is only 12 minutes long), I would just like to be able to view it on other computers or DVD players at the original quality.

It seems to me that playing it from within iMovie should be *worse*, because iMovie is not only displaying the movie, it has to render it from scratch in realtime by zooming and panning on the photos. So an exported version (i.e. precalculated, prerendered) of the same quality would certainly be playable on a normal device like a DVD player.

Can anyone explain? Or (but I doubt it) could anyone tell me what I've missed, and explain how to export a pixel-for-pixel, frame-for-frame replication of what iMovie apparently effortlessly displays??