Lowering this to zero crashes c4d r15
I was just about to post this, good find!
Funny, I have logged it already. I found it this morning, and I KNEW I should not set it below 1, I just wanted to see what will happen 
We will try to fix this in two places - Krakatoa should clamp the value to 1 internally, and the UI should also be limited to 1 so people know what makes sense.
On a related note, NEVER set the Exponent of Final/Lighting pass or Emission Strength below -32 or higher than 32. It controls the number of zeroes after or before the decimal place, and asking for numbers with 32 zeros is a bad idea. Krakatoa will render, but very slowly, and the result won’t be usable. We will look into all controls in the near future and make sure they are all limited correctly to valid ranges.