GLOSSARY
Super Black limits the darkness of rendered geometry.
The scanline renderer uses the value of the Super Black preference as a threshold for the darkness of the rendered scene.
For example, if you’re rendering a heavily shadowed object against a black background, the background will be rendered as pure black, but even the deepest shadows on the object will be no darker than the intensity level specified by the Threshold spinner (default is 15).
This option is used for video compositing. When compositing, you need pure black for the background, but all the overlaying object needs to be less than pure black so that you can still see exactly where it is.
Also, some video systems have problems with black that has RGB values of 0,0,0 and consider it an "illegal" color.
Unless you’re sure you need it, leave Super Black off in the Render Scene dialog.