There are no grey lights in real life, in Poser do exist.
If you illuminate a white sheet of paper you can dim the light and sheet will not turn grey, it will continue to be white until the moment that all become so dark that you see nothing.
In physics exist a difference between a white and a grey object. A white object is one that reflects 100% of the incoming light energy, a black object is one that absorve 100% of the incoming energy reflecting 0%. A grey object is something in the middle of a white and a black object, so it absorve something and reflect something.
If an object is white or grey is defined by the absortion coefficient and do not depend on the illumination intensity.
In the RGB illumination model if something is grey or white depend on the illumination intensity.
In some way that I cannot explain, human eyes follow the physical model and not the RGB illumination model, and this has nothing to do with rods and cones.
If you know the incomming energy and measure the reflected energy, you are able to find the absortion coefficient and so, know how grey is an object.
Our eyes receive the reflected energy, so we know its intensity, but how our brain gets the missing parameter that is the incoming energy to complete the calculation???????

The difference between rendering and real life is not the complexity and the number of variables, some real life scenes can be very simple with only one light source, a simple geometry and texturing, so it is nothing difficult to model and render the scene. You can use 3dsMax, Maya, a ltt of shaders and whatever you want, but when your eyes looks at the rendered scene will find that is artificial even it is technical and mathematical perfect.
The difference between real life and rendering is some missing parameters that just make this difference.

Stupidity also evolves!