If you are taking fotos indoor, the light there will be of a different temperatur and colour than the light outside. This can lead to interesting colour effects, but aside of those effects, you normally want to capture the whole scene in a constistent light. The white balance can not handle two kind of lights so you will have to adjust the scene flashing (which won’t help always) or covering the windows completely or with coloured material. If you don’t want or can’t to do this and you only have some highlighted areas with the light you don’t want, there are possibilities to adjust this light colour in post processing with GIMP or any other decent image editor. Here are the steps I used to correct the bright areas in the lower part of this photo of a staircase in paris.

The photograph with and without light adjustment

GIMP Layers

1. Determine the colour you want to use to adjust the light. You can use an average colour of the while image or part of the image which fits best to the surroundings of the areas you want to correct.
2. Create a layer with layer mode “Color” overlaying the background layer.
3. Determine the areas you want to adjust. Create a black layer coloring it white where you want the colour correction to be applied. This can be done using the “Threshold” tool or something similar. The use of the channel of the colour you want to adjust only, in my case the blue channel, may give very good results. If you have too much time, you can do this manually, too. Smooth the edges using Gaussian Blur filter and use this layer as layer mask for the colour layer you created before.

The layer mask used, before and after blurring it

This photo on Flickr.

Any comments welcome.

Update: Interesting, John Arnold of Photowalkthrough.com is doing the same with a similar technique in lightroom in his latest podcast.