That’s a tough one. What I did (and I am by no means an expert, and this was a quick fix–there are probably better ways to handle this) was to go into curves and boost the low end quite a lot. Unfortunately that also boosted the noise, so I ran a selective Gaussian blur to smooth out some of that noise. I uploaded the pic to my Flickr account–let me know if you want me to take it down. I don’t have a pro account, so this is just the biggest size available, not the original. I can email you the edited original if you want it, just let me know. Hopefully someone with more extensive knowledge of Photoshop/GIMP can help out!