I have a very important image that was shot by someone else, and it is greatly underexposed. I thought I could just lighten it up in Lightroom, but when I do it is noisy like an old TV, and its shot in JPG which makes matters worse. If someone out there has the tools and the time to make this image useable I would greatly appreciate it. PM me if you are willing to help.
I'd be curious to see how things turn out. An underexposed image *will* be noisy, and pushing the epxosure in PP will simply make the nosie that much more visible - it's an age-old problem in photography (even if the specifics differ betwene film and digital). My basic approach would be to push the exposure but not quite as far as I might really want, then apply a curve to bring out the area of the picture I most want brighter still, while pushing the shadows back down again, and then apply as much NR as I can stand (usually lots of chroma but only a little luminance). But being JPEG is really going to limit how far you can push things without pretty obvious artifacts showing up.