Have you sorted this yet?
I added the first person level to your empty project, and this is what I get
Have you tweaked something in the project settings? 
This is what I see in a new project
Even in a blank empty level
I get an error when I start the project about VSM being enabled, but not SM6. I enabled that and everything was ok. This is your material on a plane in the first person
Maybe update the engine, I see you’re not on 5.4…
Nice, but still cyan very desaturated, even with black scene? Why does the black scene version look a bit more like what @LilTeej seems to intend? Shouldn’t there be no difference with only emissive output (bascolor=0, no AO)?
Here I’ve tried to put the result of my previous post into open office to find a total transfer function from linear (values put into “emissive color pin”) to final sRGB image values.
(using 20 rings, data transport gamma was set to 3).
So no wonder @LilTeej 's texture image is problematic.
Unfortunately this isn’t sorted yet.
Woahh that is bright 
I didn’t tweak anything in project settings (for the project I sent you), however it was 5.0 project, so importing into 5.4 probably caused whatever happened. I’m not able to update to 5.4, my project is too far developed in 5.0 to make the risk of upgrading being worth it unfortunately
Your fresh project in 5.4 with the black scene does look closer! It’s still not 1 to 1 though which is unfortunate.
This is exactly why I’m confused, I’m not sure why with all effects disabled, and only emissive output from texture, there is any difference at all. I’m pretty sure it should be exact
So if I’m understanding this correctly, you’re saying that Unreal is interpreting linear values to final sRGB incorrectly? And something along the conversion is inaccurate? Sorry, I’m not super knowledgeable in this area. Other than some hacky thing like manual gamma correction in the material itself, do you have any ideas on how to fix it?
If you can fit both engines on your system, you can try 5.4. The .0 version is always pretty buggy.
[Left] Empty Scene | Source Texture [Right]
Material
I tested in a blank 5.4 project, with auto exposure turned off, and a post-process volume with all settings off, and the result is still far from matching the original texture (it looks much more desaturated and blurry). I’m stumped!
This is image is still in the 5.4 blank project. No bloom, no post-process, no auto exposure, just an unlit material. Disabling the tonemapper made it even worse
Well if you’re asking that way, it seems to me that unreals default is so very far from what could be called “neutral”, that real world photographers have a hard time to get similar results. My personal preference would be to have a more neutral engine, with such special effects probably applied later.
As a first experiment, I’ve tried to make the overall transfer function more neutral by setting
pp-volume->Color Grading->Global->Gamma to 0.7 instead of 1.0
With this setting, the camera is much more friendly to your texture content, and the scene appears much more like whaat a photographer would expect to see in a direct sunlight scene. But it’s also easy to get that this setting is probably less mainstream user friendly.
Or maybe, with some more complicated gamma settings
global: 0.7
shadows: 1.4
mid: 1.2
highlights: 0.6
it begins to become more difficult to notice for both, emissive texture colors and original default appearance.
But the transfer curve propabaly isn’t as smooth as it should.
Maybe someone at unreal knows better “back to neutral” pp-settings.
I’m grateful for your help, thank you! You’re right, editing the gamma in PP seems to help a bit, although it’s still not 1 to 1. I’m perplexed as to why an unlit texture can’t be 1 to 1 when both PP and tonemapper are turned off. I have a hard time believing I’m the only one running into issues with this, but maybe I’m just pickier and most people don’t care about differences like these?
To me its frustrating to make something in external software, import it into Unreal with no effects enabled, and it being quite different from the source.
Of course, and it’s also difficult to foresee how content might appear and how to work against probably issues that might arise.
On the other hand, it’s good that emissive color doesn’t seem to be handled any different as remissive color. That could be even more confusing. And relative to 3D gameworld (where remissive color is the typical thing), you made a relatively specific light (that probably shouldn’t look any diffrent than surrounding remissive scenery, when viewed through, for example, reflections in a water surface).
Here’s a full 1:1 solution:
Just make your own, new tonemapper material, making sure material domain is set to “Post Process” and (a little but further down in the material details, in the Post Process Material section) set “Blendable Location” to “Replacing the Tonemapper”.
Finally, in a postprocess-volume details, add the new tonemapper material to the pp materals array (found under “rendering features”).
Awesome/creative solution, that is 1 to 1! It does change the rest of the scene pretty dramatically however, so I may just have to deal with the visual discrepancy. I wish I could isolate this to only affect emissive materials so they are accurate. Maybe I could use Custom Stencils to apply this to specific objects.
But regardless of what I do for my project, I think you highlighted that the issue is the tone mapper and how the colors are converted. Why this isn’t considered an issue is beyond me.
Thank you for the assistance, you’ve been incredibly helpful!
Funny. That version is still not “separate path”-like enough for you? It didn’t even have some auto-exposure, so playing with sunlight intensity made everything except for the emissive textured light heavily depend on sunlight, whereas the exmissive textured light rock-solid remained to appear the same.
Here they have some documentation about how to get bloom+auto-exposure back.
Sorry, to clarify I meant that I thought the emissive texture looked perfect with your tonemapper replacement solution. It did affect the rest of my scene a lot (probably because I don’t have a directional light in the scene, intentionally so).
I’ll check out the documentation you linked to regain bloom/exposure, and see I can tune it to get the best of both worlds
Maybe at least during content creation, it’ll turn out to be a good choice to not always use a tonemapper. And also for a final result, the world has existed so many years with cameras approximating neutral reproduction (even worse: as a goal!).
Many thanks for asking your good question! It helped me to learn a lot!
Here’s a text decribing what the Reinhart tonemapper might do. I myself haven’t worked through the text, but just scrolling through the text shows how obvious it is that algo does something that’s not always useful.
