a = 0.18
Description
Tone mapping is a technique for scaling colors to a 'reasonable' level for an image.
Comparison
These pictures were all done with 100 samples per pixel, shadow rays, and tone mapped with different key values.
a = 0.18
a = 0.32
a = 0.76
a = 1.0
These images are probably darker than they should be. My code was already scaling colors down just before outputting them. I forgot to remove this so now the image still gets scaled down after tone mapping. I will fix this and post new pictures as soon as I have some free time. (Probably mid-summer at this rate.)