Hi fellas any help with the black dots on the render below? Found some info around the web but nothing helped me out (it was an old stuff in fact). Really dunno what could causing this...
By default cycles samples one lamp at a time. The black spots likely correspond to samples where cycles was attempting to sample lights which are doing nothing for actually illuminating the visible objects.
You could try disabling Multiple Importance Sampling on lamps/materials you know won't contribute much to illuminating the scene, and/or play with the Light Sampling Threshold in Properties > Render settings > Sampling.
However, if that doesn't cut it, then you can use the Branched Path Integrator, which allows for sampling all lights at once:
Note that it works a bit differently from the default integrator, so try playing around with the settings to see what works.