Hi Scientist.
I realize that the UV filter was to keep UV out of his light meter. I was trying to explain how it isn’t necessary. (had a little typo there sorry).
I also realize that this is a flashlight forum, and that most people aren’t interested in this — in fact they probably won’t be reading this far down. My comments were directed at djozz or anybody who is interested in/might attempt this experiment.
The detector simply drives a current proportional to the incoming light. In fact they give you an example circuit right in the datasheet (it looks like about a dollar or two in parts). Coincidentally, the setup is very affordable and well within the budget range of somebody who can afford a fancy flashlight.