Samples per pixel: min=2, max=64. Render time is 0:11:57. I used 32 light samples, 4 samples per hit, Adaptive Sampling Threshold = 0.005. The color of the spheres edge has been fixed.

Samples per pixel: min=2, max=64. Render time is 0:14:40. I used 32 light samples, 4 samples per hit, Adaptive Sampling Threshold = 0.005.

Samples per pixel: min=2, max=64. Render time is 0:15:51. I used 16 light samples, 8 samples per hit, Adaptive Sampling Threshold = 0.005.

Samples per pixel: min=2, max=64. Render time is 0:02:27. I used 8 light samples, 2 samples per hit, Adaptive Sampling Threshold = 0.001.

Samples per pixel: min=2, max=64. Render time is 0:02:27. I used 8 light samples, 2 samples per hit, Adaptive Sampling Threshold = 0.001.

Samples per pixel: min=2, max=64. Render time is 0:02:27. I used 8 light samples, 2 samples per hit, Adaptive Sampling Threshold = 0.001.

Samples per pixel: min=2, max=64. Render time is 0:01:59. I used 4 light samples, 2 samples per hit, Adaptive Sampling Threshold = 0.01.

Samples per pixel: min=4, max=128. Render time is 0:04:23. I used 8 light samples, 4 samples per hit, Adaptive Sampling Threshold = 0.005.