Overview of Mental Ray
When on, creates a mental ray for Maya area light. This option is disabled by default.
When on, the size of the mental ray area light does not factor into the intensity of the light.
This is the shape of the area light source. Select from the drop-down list: Rectangle, Disc, Sphere, Cylinder and User. The default is Rectangle.
This represents the number of sample points emitted from the light (X and Y). The default is 3 and 3. Values greater than 3 increase the quality by reducing graininess, but may increase rendering cost.
High Sample Limit
To reduce rendering cost and time, it is not necessary to use a high number of sample points after a light ray has been reflected or refracted several times. This attribute represents the number of bounces that the light ray should go through before it uses the Low Samples values instead.
The default is 2 and 2.
This can be used if you want the area light object to be visible when rendered. The default is off.