Gotcha. What could honestly go wrong if you dont have one though? uh oh light burn *lowers intensity* ...and scene.OOOO Bull Shit!!! It takes years to master reading plants and knowing ones lights and what they can do and how to use them. And as fast as tech changes I will take all the help I can buy, beg or borrow. Good mechanics use good tools and all the tools they have at there disposal. I would have given my left nut to have this meter in 1975 when I started.