Ambient light by default in Cycles?

Support Lighting and Rendering
1

I am reading a book by Jeremy Birn on Lighting and Rendering and it mentions that most 3d programs have an ambient light included and that it is best to turn if off. This can flatten a scene. I noticed that Blender Cycles is not completely black in the rendered scene. Even when deleting all of the lights it seems to be gray.

Does anyone know much about this subject in Cycles and what the best way of working is?

2

World and world color affects the amount of light. Either delete world or change the color to full black and it won’t add light.
Although, if you replace the color with an environment texture, you can use image based lighting instead of (or in addition to) lamps.