When you first open Hypershade, three nodes are available by default in the Materials tab: lambert1, particleCloud1, and shaderGlow1.
Use the Shader Glow node for environment glows.
Shader glow from one surface can affect the intensity of another surface’s glow. For example, a large glowing surface that enters a scene may appear to cancel the affect of, or alter, the glow of a smaller surface in the scene. This phenomenon is caused by the Shader Glow’s Automatic Exposure setting.
To get the right glow and halo intensities using Shader Glow
The glow intensity normalization factor and halo intensity normalization factor are printed in the Maya command shell or DOS window. They look similar to this sample:
glow intensity normalization factor = 0.0110171.
halo intensity normalization factor = 0.0243521.
These are the values Maya uses if Auto Exposure is turned off.