What Is Tone Mapping?
Now we move to the digital space. It’s a lot easier for us to see these bracketed shots on the back of an LCD, and the production of the image costs us nothing as we just download it. What of these extra images? In HDR, we use them to create an HDR file: a file with more range than what we are capable of seeing in a frame. Because all this tonality is very hard to see in one space, we use software to take the tones of the image that are not visible and map them to areas that are in fact visiblea process called tone mapping (see Figure 3).
While I was sitting and looking at the sliders of a tone-mapped image, I noticed that the movement of the sliders in one direction versus another did not only change the overall tonality of the shot, but changed the colors of the image. The overprocessing of the tone-mapped file is usually what is derided as being “fake” in a tone-mapping sense, but what if we took that overprocessing to the extreme? How would that affect the overall range of the file?
Moving the sliders further and further, I noticed that specific portions of the image were being tone-mapped a specific way, while others were tone-mapped a completely different way. Colors appeared to separate these regions from one another, creating almost a visual way for you to see what kinds of regions there were in the image, and the interpretation of tone in it (see Figure 4). Now, we have used the overprocessed image not as a completely different work of art, but rather as a colored guide of how to tone an image in black and white. At this point we can save this image.