Touch Up Dark Photos

Open the photo you want to make lighter. I am using the photo I got off the internet below:

Dark Photo

First thing you need to do is to duplicate the layer by clicking Layers > Duplicate Layer:

Duplicate Layer

With the top layer selected, click on the arrow by the set blend mode for layer to access the drop down menu and select screen from the menu options. Adjust the Opacity to your liking.

Screen Mode

Here is my photo after setting the blending mode to Screen:

Before
After
Dark Photo
Screen Mode

Photoshop CS5 Tutorials