Render gets darker as camera moves towards model

I downloaded a very nice free model of the Earth from Turbosquid but I have this weird problem where the render gets progressively darker as the camera moves towards the model.


Close up:

There is only one lamp - a sun, directly in line with the camera. The model has several materials/textures - atmosphere, earth, clouds, shadows etc. I tried contacting the artist but Turbosquid does not support free models.

Any idea what’s causing this?


EDIT: Ok it’s compositing nodes, which I wasn’t familiar with but will be any time now :slight_smile: