There are a few default settings you may not be accustomed to that effect the maps you’re using with Arnold. The Arnold Standard Surface material defaults to a Base Color Scale of 0.8 which means that any texture maps loaded into the Base Color slot will appear darker when rendered. To fix this, simply set the Base Color Scale to 1.0
As this is a frequently asked question we have provided both the question and answer in this thread.
Btw someone has to say it.. - it doesn't make any sense to have a diffuse weight (scale) set to 0.8.
If you set the default diffuse color for example to an off-white (0.8,0.8,0.8) it's like you set that because is convenient to have it as a default color, not fully white but bright enough to be a good choice for an initial lighting/shading setup.
However if you set up the scale to be 0.8 is a different thing. It's no more a color choice, it's like you're saying.. our materials have a dimmed albedo by default. And why on earth it should be like that ?
More over, every damn time a user plugs a texture/shader/color in the diffuse color he has also to set the scale back to 1, that would not happen instead with a default diffuse color as you already realized.
And frankly 🙂 if you answer your own questions for the purpose of being clear that's ok.. but if you answer your own questions just to pretend you're not weird.. well .. cough cough.. it's not so ok 🙂
I completely agree, I don't personally see the point in having scale set to 0.8 by default. For users not realizing that it's been set this way, it can be terribly frustrating. That's especially true for users bringing textures in from applications such as Substance Painter or Quixel. The first thing I do when I start a new material in Arnold, is set all my Scales to 1.0. For this reason, and because I really would want everyone to do the same, I posted the Q&A. I'm also a moderator trying to be helpful and most definitely weird ;).