Linear workflow setup

[The3DNut]

Update: When I change the diffuse material color to R: 0.5 G: 0.5 B: 0.5 (HEX BCBCBC) from RGB 0.216 (HEX 808080) then everything seems to render correctly



So I guess the problem was that it was set to 50% grey prior to being gamma corrected. My own tests were setup properly though and not working. Oh well, I am sure I will get to the bottom of this eventually.
I would still like to know about the question of whether or not any node is absolutely necessary between the VRayMtl node and the Material Output node.

Thanks again for your help.

[The3DNut]

Here is the only thing that seems to be working for me, which is definitely not a "set it and forget it" approach:

Color Mapping: Defaults with the only change being Gamma set to 2.2
Color Management: Defaults
Linear Image Usage: In the Properties Shelf>Bitmap Settings, set to Linear in both V-Ray Settings and Image Settings.
Gamma corrected Image Usage: In the Properties Shelf>Bitmap Settings, set to Gamma corrected in V-Ray Settings and to Linear in Image Settings.

On the upside, everything makes sense to me...except for why the Gamma correct image has to be set to Linear in the Image Settings in order to match a linear image in the UV Image Editor.

[The3DNut]

Alright, I think I solved my issues. I thought I had it figured out but then when I tried an sRGB image in the scene it was giving a double dose of gamma in the render and in the UV/Image editor.
Once I got the sRGB correct and I used it as the foundation I realized that my linear image and my material were both wrong also even though everything was matching. What messed me up in this whole process? Two things really: 1. Setting a Linear image to Linear in the Bitmap settings. 2. Setting the RGB value to the color I want instead of setting it in the HEX value.

Here is what is working for me, and now working correctly:
Color Mapping: Defaults with the only change being Gamma set to 2.2
Color Management: Defaults
Linear Image Usage: As mrG_Grm stated already, in the Properties Shelf>Bitmap Settings, set to sRGB NOT LINEAR in both V-Ray Settings and Image Settings. (Seems like a bug to me)
Gamma corrected Image Usage: In the Properties Shelf>Bitmap Settings, set to sRGB in both V-Ray Settings and Image Settings.
Diffuse Colors: in VRayMtl, set the diffuse color with the proper HEX value (ex 808080 for 50% grey). The RGB value will be different because of the gamma correction

[The3DNut]

P.S. it also works to change the color corrected image in the V-Ray Settings from sRGB to Gamma corrected with a value of 0.4545 (0.455)

[mrG_Grm]

I guess thats what is your concern. Single material node, back then, was a node that determined what kind of material you are using e.g. Two sided, single sided, toon, bump etc. Now it is implemented in single node called Standard Material.