Render with default lights, after lighting
Start a new scene. First go to Views->Viewport Configuration. In the Rendering Method tab be sure under Rendering Options that Default Lighting is checked, and 2 Lights is selected, Otherwise, this will not work! Then hit OK.
Then in the menu go to Create->Lights->Standard Lights->Add Default Lights to Scene
Be sure that both Add Default Key Light, and Add Default Fill Light are checked. Also set the Distance Scaling to 1000.0 (this will allow the lights to work for a scene that is in any location with respect to the lights). Then hit OK.
Now your scene has the default lights in the scene. Save this file as your default lighting scene. Now you can merge these lights into any scene you want. After you have merged these lights into your complexly lit scene here is a checklist to be sure that when you render you are just getting the default lights:
•Turn off all of your Indirect Illumination (mental ray)
•Turn off any exposure settings you have (don’t worry, your settings won’t disappear)
•Open the Light Lister, and turn off all of your lights, except for the DefaultKeyLight and DefaultFillLight
Now when you render, your scene will be lit just as it was before you added any lights (even though you have all of your scene lights still there)! Of course when you want to render your scene with lights, then turn everything in the list back on, and turn off the Default lights.