10.4 Special effect attribute

Iray uses the default attribute coming with the default Maya camera to control motion blur.
Special effect attribute
Shutter Angle
Controls the blurriness of motion blurred objects. In a real-world camera, the shutter is actually a metal disk that is missing a pie-shaped section. This disk sits between the lens and the film, and rotates at a constant rate. When the missing section is in front of the film, it allows light from the lens to pass through and expose the film. The larger the angle of the pie-shaped section, the longer the exposure time, and moving objects are more blurred. Shutter Angle is measured in degrees. The valid range is 1 to 360. The default value is 144. This attribute has no effect until Motion Blur is turn on in the Iray Render Settings.