Just watched this video and was wondering if we could implement this for ue4, does ue4 even use sRGB for rendering? Here is the video https://www.blenderguru.com/tutorials/secret-ingredient-photorealism/
UE4 already uses HDR by default, and clamps it down to LDR using (mostly) the post processing settings. You can view the histogram by using VisualizeHDR. Also 4.15 added a filmic tonemapper that mimics the desaturation in film talked about at 22:10.