3DSMAX 2015: Light problem in zooming animation

Hi guys, maybe someone could help me with this problem.
I’m working in 3ds max 2015 and I have to create some zooming animations: unfortunately sometimes, while the camera is moving toward to the object but it is still far away, the lights and shadows on the object become dark randomly and every frame has a different light result.
Also with static renders I have the same problem, when I’m far from the object It becames darker.

Both mentalray and standard materials have the same problem.
I attach an example with 3 frames of a simple animation.

Thanks in advance.