Yes, but to expand slightly:
DVDs can store data in several ways. The main ones:
- Video to be displayed on a TV. This can only be NTSC (for the US). BluRay DVDs also handle HD, provided you have a BluRay recorder, and a BluRay player to play them back.
- Computer files to be read on a computer. You can store any file on this format, and images can be stored in any resolution. Basically, this type of DVD can be read on a computer. DVD players (the sort you connect to a TV) can sometimes read them, but usually not. Just to confuse matters, you can also write computer files in this way on a BluRay disk (if you have the appropriate BluRay writer on the computer), but that just makes them bigger (they store more data) - you can still write any type of file to them.
Normally the whole DVD is written in video format or computer file format.
So if you are creating a slide show that writes to the DVD in video format, and plays as a video on a TV, then you're limited to NTSC resolution on a normal DVD, or HD on a BluRay.
If your slide show program creates the slide show in a normal computer file, and it's going to be written to a DVD in compute file format, then it can be any resolution, provided the program creating the slide show supports it, and you're going to play it back on a computer (or you have a DVD player that can cope with that type of file connected to the TV - as I say, most TV DVD players don't).
However, I don't know anything about Fotomagic or iDVD (or Macs, for that matter) so I may be giving you incomplete and misleading information! With luck, and expert on those will be around soon to give more info.