[Zeke]

It's not easy to find and this is in general for stairs, closets and corridors as well as door exits:
“five lumens of light measured in the darkest corner” Cal. Code Regs. tit. 22 § 73651
There are also specifications (lots) for emergency illumination and signage. And if you keep looking, there are job site requirements, warehouse, factory, etc.

The "darkest corner" would be rather subjective on a front porch. Furthermore, all of the residential applications can be switched. Therefore, the amount of lumens is a moot point.