In a frenzy of web activity the other day I ran across a photoshop plugin that isolated all the dark/shadow/underexposed areas, created a mask or layer showing the varying degrees of dark (like a blurry grayscale watercolor) leaving well lit areas completely alone (like sky).

Then you could adjust just the shadowy bits. Click, click, done.

While I appreciate in advance how "easy it is to do that without a plugin" type responses, what I'm asking for is if anyone knows what plugin I found and help me find it again.

Even links from www.lmgtfy.com would be appreciated since my last attempt at nailing the perfect search terms failed.

And no, it's not in my history either. I really just need help with the name/website if anyone knows what I'm talking about.

Thank you!

While not exactly what you are looking for, Adobe Camera Raw (version 4.6) has a "fill light" slider that can quite helpful in lightening only the darker portions of the image.