Thanks Derjyn 
Edit for @Derjyn : Jeah its used with 4.15. And the brightness problem is fixed and you the brightness from the tonemapper / eye adaptation can be changed to nearly fixed values.
The polishing and documentation part is the most time consuming thing right now. Its crazy, trust me. But that makes a huge impact on how this effect can be used. This Post Process can be used in conjunction with Post Process Volumes and it even saves and reads Templates!
That´s so convenient. Its a simple trick with the construction script but that will make you soooo happy, i promise. It reads and writes values from the Retro Rendering Postprocess and from the Post Process Volume. But this is just a service, you can also use this Post Process Materials within the regular workflow. Its all blueprint stuff no c++ code.
The reason why this is still filed under this Retro Game thread is that it will be used in my own projects. This makes sure, that there is a use for it in a real content creation workflow. It doesn’t replace real pixel art but it can be used to render out Art assets that have a specific look. Combined with a render blueprint, this can be used to create isometric art like seen in many old isometric games. I don´t know if this can be applied to this sidescroller game type yet so that needs to be tested.
There is also another reason why i really like using Unreal Engine for rendering instead of non real time rendering, and that is the openness of the art creation workflow. You can use every program to make 3D Models for the Unreal engine and than render out your asset with this Retro Effect applied with so much customization on effects and on materials in real time. No need to to use any other Render engine if you can have PBR rendering in realtime for this task. This will be a very creative workflow and i can hardly wait to use it for my own projects.
And for all who downloaded or bought my Gumroad version, this pack is now a much more polished and fixed version. Its not comparable anymore.
One more Teaser on how this can be used for retro looking cutscenes :
https://youtube.com/watch?v=3eFD4G7zGwk
Cheers,
Mathias