There's more...

There's something useful we haven't seen yet, as it requires the use of other software apart from Unreal, but I want to mention it before we move on and that is the concept of Look-Up Tables (LUTs), and they are an asset that allow us to match the post process tweaks we make in other software such as Photoshop or Gimp in Unreal. 

Think about this – you have an image in Unreal that you want to tweak. You can do so through the methods we've seen before, by modifying and tweaking the post process volume and playing with its settings until you get the effect you are after. However convenient that can be, some users might feel more comfortable taking that image and pasting it in an image editor and adjusting it there. Fortunately for us, this process can be replicated thanks to the LUTs.

The way we would do so is by following the next steps:

1. Export a sample screenshot out of Unreal that shows your scene clearly.
2. Load that sample shot in your image editor of choice, alongside a neutral LUT image. One such asset can be found on Epic's official example, which you can find at the following website: https://docs.unrealengine.com/en-us/Engine/Rendering/PostProcessEffects/UsingLUTs. The idea is that all of the changes that you will implement in the next step are applied to both your sample from Unreal and the neutral LUT.
3. Adjust the image however you like change the contrast, the saturation, brightness... Any changes that you make will also affect the LUT texture.
4. Once you are happy with your image, export just the small LUT file. The modifications that the image has suffered are going to enable us to replicate that same effect in Unreal.
5. Import the modified LUT back into Unreal and double-click on it once it is inside the engine. In the Details panel for the texture, set the Mip Gen Settings to NiMipmaps and the Texture Group to ColorLookupTable.
6. After that, head back to your post process volume actor and under the Color Grading | Misc tick the Color Grading LUT checkbox and select your recently imported texture. That should leave you with a scene looking exactly like the one you modified in your image-editing software.

As you can imagine, this technique can be quite useful – especially for those users who are more used to adjusting these types of settings outside Unreal. However great that is, it also has some shortcomings that we should be aware of. Even though we won't cite them all, they all revolve around the notion that LUTs don't translate well across several screens. Even though you might be doing a correction to your particular scene and you might be happy with it, due to the nature of these textures operating in a low dynamic range those changes might not translate well into other displays—especially those using a different color space. Keep that in mind when you work with them!