With Photoshop CS3, how do I balance brightness in a photo with a sunny window in a dark room?

Not sure how a gradient mask would help with this sort of shot. (Would make more sense for a landscape where the sky was too bright and the ground too dark.)

I did come across a way to use a Gradient Map adjustment (if such exists in CS3):

- Duplicate your image onto a second layer (e.g. drag Background layer onto "New Layer" button).

- Set Foreground color to 25% gray and Background color to black.

- Image > Adjustment > Gradient Map the upper layer, using a Foreground → Background gradient.

- Set upper layer to Color Dodge blending mode.

You can play with the gradient (colors, midpoints) to get different results.

Something else you can try is to selectively apply an adjustment layer such as Exposure, using a mask:

- Open the Channels palette

- Ctrl+click on the RGB (all colors) channel to make a selection from the channel

- Invert the selection (Ctrl + Shift + I), in effect selecting all the dark areas

- In the Layers palette, add your choice of adjustment layer. The selection will become the adjustment layer's mask.

- Tweak the adjustment layer settings as needed. (Using Screen blending mode may also help.)

Noise might be unacceptable if the original colors are too dark, since there are fewer steps of color to work with. You might also find other interior shadows being lightened too much, although you can play with the layers and masks to mitigate the effects. It certainly won't be perfect, but pretty decent results with what was given.

Didn't see what Arturo suggested, but I suppose it was something along the lines of "retake the photo with flash or covered windows", which indeed would have been the best thing to do. Using bracketed exposure could have also helped.