What resolution is the camera capable of?
Each of the pictures in iPhoto should be at least 5MB, possibly much greater, and when you exported the pictures to the DVD you "may" have selected an extremely low resolution.

On the DVD, what is the size of each picture compared to the size of the original file in iPhoto AND the Memory card?

If the picture size is markedly different, then something was incorrectly set when you moved the pictures to the CD.

Let us know the answers

P