As my DP1 RAW files aren't read by Aperture I process them in the manufacturer's software SPP. This does a very good job as might be expected but is painfully slow and it's not really a program for managing large numbers of images. SPP does offer some additional adjustment capabilities though, one of them is Fill Light. Other programs have fill light capabilities but they're different.
The Fill Light adjustment has both positive and negative capabilities. Positive fill light approaches a somewhat HDR effect. Negative fill light adds a dream like quality to images, it's fun to play with. The impact is most pronounced around the lightest part of the image.