I have searched and found some abandoned threads explaining how to key frame photon intensity.  I still don't get it.

I am using MAYA 15. 

When using mental ray and an area light emitting photons, I would like to grow the light intensity from 0 to something close to regular lighting.

I have a dialectic material, caustics, and final gather in the scene.

My goal is to keyframe either photon intensity or the light intensity using maya/mental ray.

Can some one help?

Thanks in advance.