Up until this point, the HDR process has been completely turnkey – follow the steps, get an HDR image. Here, however, things get personal and artistic vision comes into play as you take your HDR file containing a huge amount of brightness information and map it back to something that can be saved as a normal JPEG and displayed in a normal monitor. This process is called “tone mapping” and it’s where an HDR image becomes what people tend to think of when they think of HDR images.
Tone mapping in Photomatix (which I will consider since it’s the tool I use) involves mucking with the values of 15 different sliders which control various aspects of the conversion. The settings for every image are different so it’s not possible to give specific values that will always generate the kind of image I produce. Instead, I will discuss the settings and indicate roughly what each one does and how much effect it has on the final image. I should point out that I have pretty much no idea of the mathematics behind these sliders – my descriptions are based purely on fiddling with them and observation of the results. I would encourage you to do the same.
The mechanics of tone mapping an image in Photomatix are pretty straightforward:
That’s it – you’re done. Well, more or less. Perhaps it’s worth considering those pesky 15 sliders and what they do since, as I mentioned back in part 1, you can tone map a single HDR image in thousands of different ways and come up with completely different results. Just to prove my point and to whet your appetite for some slider info, here’s the example image I am using throughout the tutorial tone mapped with four different sets of parameters. Don’t worry – I’ll provide the actual parameter sets used for each mapping in the final part of the tutorial. Click on each to go to the image on Flickr where you can see the original, high resolution versions.
Moving on to the final part of the tutorial, I’ll let you in on the parameters sets I used for the four example images above.