settings

Software:
Blender 2.79

A quick Cycles rendering tip:

There are situations in which we need to render an animation with changing lighting complexity, and as a result, parts of the animation need more samples than others to be effectively rendered.
For example when the camera starts it’s movement on the outside in an exterior scene, and moves into an interior space like house or a cave, or a vehicle, in many cases, the exterior part of the animation can be rendered with much less samples than the interior part.

In such cases, rendering the whole animation with the higher sample settings will demand unneeded render time in the simpler parts of the animation.

One possible solution would be to simply render the animation in two separated render jobs with different sampling settings, one for the less demanding part and another for the more complex part and than append the two parts in an editing / compositing software. but that requires more work on the shot, more management etc.

A simple solution is to animate the sample settings in Cycles.
Make tests at different times along the animation to determine how many samples are needed at each part, and key-frame the settings accordingly.