Yes, when I see them from the camera screen, they have good quality... I don't think it's a jpeg preview.
This is my situation: my camera creates PEFs files, which I converted to DNGs with Adobe DNG converter. Then I opened them in aperture, and I tried to work with them. So I learned something about Aperture 3, then I saw some videos on the apple site, in the aperture 3 page, I quickly read the manual in the section of the image editing, but I'm not new to Exposure, Brightness or Contrast. I've modified photos with other programs (also with photoshop, but I'm not a professionist...). When I had moved from iPhoto to Aperture 3, I liked it a lot, because I could do lots of thing with my photos and my new camera easily. Until today everything has gone well, but when I installed the Camera RAW update 3.1 from Apple, Aperture started to convert new photos with the new convertion settings. If I take a photo imported in Aperture 3 before the update, I can reprocess it, and when I do this, it becomes darker. Here's an example (converted to jpeg):
http://img690.imageshack.us/g/beforeg.jpg/
Is that normal?
I'm sorry for my bad english... When I used darken in this thread, I meant darker, not darken... I'm sorry.