I see you've had no replies yet. I would have posted earlier, but I'm not a Mac user myself and so i am not at all sure of my facts.
That said, I suspect the issue would be the same with Windows systems.
The problem is, screensavers use code within the Operating System itself to produce those 'cross fading, zooming, cropping' and other effects that you see, and they are nothing to do with the separate images themselves.
In Windows OSes we need to use specialised "Presentation software". An example would be Microsoft's own Office Suite Powerpoint software. With Powerpoint you can make image slides with all those screensaver effects, and probably more.
I don't know about iMovie, iDVD and iPhoto, but I suspect you need to find specific Presentation software for your Mac, perhaps like iWork's Keynote, as described here;
If not that, try a Google search, (or your favorite search engine if different), for Presentation software Mac.
I suspect you will need to create the presentation first, before burning, (copying), that file and the images, to a DVD,
Alternatively, why not repost your question in one of CNET's Mac Forums, listed below. That's where the real experts are.
I would really appreciate any help I can get on this! I am simply trying to find a way to have a DVD burned of my photo screensaver slideshow on my Mac. I have tried using iMovie, iDVD, and iPhoto to make the slideshow and CANNOT figure out how to make it look exactly the same with cross fading between slides, zooming back and forth, and cropping slides to fill the screen.
Everything looks amazing with the screensaver, but as soon as I try to bring those same photos into any of those other programs and choose the same options as the screensaver (with the exception of "zooming back and forth", none of them seem to have that option, aghhhh!) it doesn't work properly, and it cuts off the tops and bottoms of the vertical photos.
I can't even believe how much time I have put into this project which I originally thought would be so simple. I have researched this a lot and still can't figure it out. Does anyone have any advice?