I have never installed DPP, but based on this thread I decided to give it a shot last night. I then did a similar test as the poster above, but under different circumstances. I had a shot that was taken at night, with some lights, and was exposed for the light. So the dark parts of the image were severely underexposed. It was taken at either iso 800 or 1600. When I tried to either increase exposure or apply fill light in Lightroom, the dark parts became very grainy. I thought just one of the issues with the way I took the shot - I'm still pretty much a rookie at some of that stuff. However, when I took the same image and did the same thing in DPP (well at least the exposure thing), I did not get the same grain - much smoother conversion. Very interesting.
However, I do have one question. Remember this was my very first exposure to DPP. I am used to Lightroom's underlying metadata philosophy - no changes made to the actual Raw image. But when I was done with the changes in DPP, it asked me if I wanted to save them. Is DPP making alterations to the Raw image? I know that even if it was, I could 'save as' and retain the original, but I'm assuming that if I just 'save', the original is modified. Is that right? Thanks