Basic Tone Mapping

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In this tutorial, some basic tone mapping techniques will be demonstrated so Kray users can get a basic grasp of what tone mapping is and how it can be used to improve your images.


We have a scene, it has sunsky in textured environment set to CIE color system (personal preference, could be any one), a 220% intensity spotlight with sunspot with 1km inverse^2 falloff. We open kray pick the medium preset, check "spotlight to area" and hit render and we get this :

Gamma11.png

That's very dark. This is with gamma and exposure 1 (which is the same as linear gamma)


So for starters we can bump up exposure to 2.0 and see what happens.

Gamma12.png

Not much better. It still is very dark plus the sky is completely burned and the floor has taken a yellow-ish color.


If we switch to exponential now and keep parameter 1 and exposure 2, we get this:

Expo12.png

You see that it looks pretty much the same, only the burned areas are no longer burned, which you might like or might not, but it tends to give the images a calmer look and preserves more shading data in really bright areas.


For now we will switch back to gamma and lower exposure a bit, since the bright areas are a little too bright. With an exposure of 1.6 we get this

Gamma116.png

Now the bright areas are kind of ok, but the rest of the image is very dark, we need to fill it with more light.


We will keep exposure to 1.6 and change parameter to 1.6 as well.

Gamma1616.png

I'd say that looks pretty balanced for now.


Let's do another small tweak, we bump gamma parameter a little more at 1.8 and lower exposure a tad to 1.5.

Gamma1815.png

Well I'd say we're done with it for now. It looks good enough.


But for testing purposes, let's keep parameter and exposure values and switch to exponential and see what happens.

Expo1815.png

Hmm, that looks completely different, than the gamma version with same settings, while when we had a parameter of 1 previously it was pretty similar. Exponential works differently in general and it's actually most useful when we have a really bright light source.


Now here is a render with exponential parameter 4.2 and exposure 1.

Expo421.png

That looks kind of like our gamma 1.6 exp 1.6 image and it has kind of duller colors in the bright areas (and more vibrant darks somewhat), which in arch viz is often a desired effect. So exponential can be useful but depending on the situation it can give strange results if we have gamma as our reference point.


Note : The images are a tad dark in general, but they should serve their purpose. Also, the values that work here will probably not work on other scenes, you have to experiment. It depends a lot on the materials and lights you have.