#3. "RE: D3000 taking very dark photos (vs. D40)" In response to In response to 0
Also check the Tone/Contrast Curve being used. Even the best of the cameras out there will not get Automatic Tone Curve correct 100% of the time. The easiest way to think about this is "You can always EASILY ADD contrast, but EASILY NOT remove it." Pick a Low Tone/Contrast curve and keep it there. Then when you're sorting photos during post-process, you can then experiment with adding contrast as necessary. This results in somewhat "flat" photos out of the camera, but more control over the image processing.