Maybe someone has a solution, so far I've spent hours trying to figure it out but I can't find a way

I make replica motocross tracks using height data from Tangram and a satellite overlay from Google maps then Google earth for high resolution images. I use these texture overlays as a guide, not a final texture.
I use 'Runtime Lighting Over Texture' so I can see depth and height accurately when shaping, but it's way too dark. It seems even worse the closer to the ground level you get, as if there is a black fog on the terrain only..
Is there any way to increase the brightness, or decrease the shading effect? I would love the 'Runtime Lighting Over Texture' to be about 50% strength max..
Or, is there an alternative to 'Runtime Lighting Over Texture' that still gives a bit of definition to the heightmap while using a texture overlay?
Thanks
