Photographs taken in bright direct sunlight typically are of high dynamic range scenes, and the resulting camera file usually requires careful tone mapping to produce a satisfactory final image. High bit depth GIMP’s floating point Exposure operation provides a very useful tool for dealing with this type of image, and of course is equally useful for any image where the goal is to raise the shadows and midtones without blowing out the highlights.

High bit depth GIMP’s floating point Exposure operation combined with a suitable layer mask can also be used to darken portions of the image, either by moving the upper left Value slider to the right (darkens the image by increasing contrast and also increases saturation; requires careful masking to avoid producing regions of solid black), or moving the lower right Value slider to the left (darkens the image by decreasing contrast, useful for de-emphasizing portions of the image).

This is a GIMP-specific tutorial. However, the same technique can be employed using the PhotoFlow raw processor and possibly other image editors that allow for 32-bit floating point processing using unbounded RGB channel values. The neat thing about using this technique in PhotoFlow is that PhotoFlow uses nodes, which allows for completely non-destructive editing of the inverted grayscale mask that’s used to recover the highlight detail after applying positive exposure compensation to raise the tonality of the shadows and midtones (even if you close and reopen the image, if you save the image’s PFI file).

_{The original tutorial this was adapted from can be and is reproduced courtesy of Elle Stone}

_{GIMP Tutorial - Tone Mapping Using GIMP Levels (text and images) by Elle Stone is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.}