GIMP Contrast mask tutorial
Method 1
The contrast mask method works very well on images, to correct the exposure of dark areas, without overexposing bright areas.
This method will work on dark underwater or normal dry land images. For underwater images taken below 5m you will need to implement an extra colour enhancement filter method, which I have written a tutorial for.
There is a Script-Fu (macro) for this tutorial, the file name is create-contrast-mask.scm and can be found on our Script-Fu downloads page. See the Script-Fu help page if you need instructions on loading and activating it.
Find one of your photos that you thought were fantastic, but came out very dark, due to not using a flash. I've used a customer's photo for this tutorial.
The first thing to do would be to arrange the various GIMP toolboxes on your desktop so that they are all accessible, as you will need to go from one to the other quite a lot. You will need the main toolbox, the layers dialogue and the image (obviously).
