(In another forum someone asked a question – actually, more like posed a challenge – related to how much usable detail and quality could be extracted from a raw file that contained areas of very low luminosity, as could happen with a badly underexposed image or with an image of a scene with a very large dynamic range. Since I went to the work of responding and illustrating my response, I figured that I might as well share it here, too. With minor revisions, here it is.)
First, I actually have a “real” version of this photograph in which highlights were slightly blown, but which I preferred to use since I could bring them back in post and get a bit more shadow detail to start with. (It looks a bit bright to me as an on-screen jpg, but it makes a fine print.) That photograph ended up looking like this:
This photograph and the other I’ll move to below were both shot from a tripod with a Canon EOS 5D Mark II at ISO 100 using the Canon EF 24-105mm f/4L IS at f/16. While the “keeper” used for the photograph above had a 1/4 second exposure, the example I’ll use below was shot at 1/30 second.
The exposure challenge in this scene was the very large dynamic range between the bright spot of sky at the head of the canyon and the much darker colorful foliage in relatively deep shadow in the foreground. Exposing for optimal quality in the foreground would completely blow out the sky, while exposing for the sky would necessarily grossly underexpose the foreground.
I originally thought that I might like to have four bracketed exposures in case that would let me produce a better final image via layer blending, but it turned out to be unnecessary and the final image (as shown above) has a single source file with no blending. However, this means that I still happen to have one very badly underexposed (by three stops) version at 1/30 second which I’ll use here as the starting point for what I plan to illustrate in this post. Follow along with me and see what I can do with the very underexposed version of the file… Continue reading Post-Processing: A Shadow Recovery Example
