Weird light fall of on spheres I've been experimenting with making planets in Blender with Cycles. However, I've run into this strange issue that I'm not even sure if it is an issue with the way that light is falling off of a sphere in Blender. I'm using a sun with a strength of 10. I've tried setting things up using just a blank sphere with no difference. I've also tried just starting over with no luck. I've messed with the max bounces, step size, and max step options. It seems as if these things aren't changing anything. Even if this is how it's supposed to work I would like to make the light fall-off more gradual. Especially in the render included, I think it really harms the look with the dramatic fall off. All hep is appreciated, thanks!
No atmosphere (Sorry I had to crop)

atmosphere
I find sun lamps to never be very realistic in many cases. Try swapping the sun lamp for a large (proportionally) area light. You might have to make it relatively powerful given the distance, but I think it gives a better look: