Ok -- you've got my curiousity up.
What do you mean by "knock off 200 frames"? How, at what intervals, and what other camera settings (resolution, JPEG Quality, etc.).
You do have very limited dynamic range with a Digital Camera compared to film. So, exposure needs to be more precise. In other words, you probably can't just pick an aperture/shutter speed combination and expect the frames to look the same (unless they are taken very close together, and the light is very steady).
What is your subject (is the scene changing)? JPEG Compression could also come into play.
Let us know more information about what you are doing, camera settings, etc.