Retouching dark and imperfect photos to get an illuminated output

We start by opening an image shown below. It has certain dark areas like the ceiling where details are lost because of darkness.

From Image menu select Adjustments>>Shadow/Highlight. Shadow/Highlight is a wonderful option that automatically improves the shadow and highlight situation in an image. You can adjust the values too. In this case default values seems to work fine for us.

Now to go a step further we'll adjust the levels. Press Ctrl+L to open level settings. Apply settings as shown.
look at the images below to compare the before and after situation. The details in ceiling are very much visible now.