(Apologies in advance to the APUG community for the following...)
Originally Posted by keyofnight
One thing to note: Aperture 3 is one of the worst tools you can be using to do these adjustments, because it does not have a simple Invert control. Instead, you have to invert using the Levels tool, when ends up reversing every other control you will be using. It absolutely sucks. Photoshop is really the best tool I've found when trying to work with adjusting color negatives, then once you've got the inversion done, you can use Aperture for the rest of your work. (I know, Photoshop is an expensive tool... maybe you can get away with using GIMP, but it has been a while since I've looked at it.) On the Mac, you might be tempted to try Pixelmator, since it is much cheaper than Photoshop and seems to be powerful. Don't. It doesn't have individual channel levels, and it only does 8 bits per channel. Worthless for this.