There's some confusion, somewhere. It's probably me. :D

But, as I understand it, the "Light Emitter" entry on a figure or prop's properties menu is only concerned with whether or not that surface returns reflected light. In other words, if it is checked, then light in the scene will bounce off of it. If it is unchecked, light will simply pass through it. This only effects light-bounces. So, you could have everything in a scene with its "Light Emitter" properties unchecked, and you would get no reflected light from the surfaces of those objects during raytracing or IDL bounces. This is handy, since complex objects with lots of facets may require more rendering time for little or no benefit. By unchecking everything like that and just using something like BB's Enviro Sphere, you can still get bounces off of that and reduce rendering time, yet retain IDL settings for good effect. (Depending on the accuracy you want.)

But, materials settings like Ambient and the like are completely different.

This is my current understanding, but I have yet to work with "Emitters" like meshlights and such in PP2012. I think the confusion either comes only from me, since I'm a noob to PP2012's lighting and materials, or because they chose to label the entry on the properties menu "Light Emitter", which is not really what that setting is for.

If I'm wrong, please correct my ignorance of PP2012 lighting... ;)

 

PS - I would love to have a script that I could use to choose to alter object/figure properties like "Light Emitter" on the fly, from a list of scene items. That's would be a nice time-saver!