What some may not know, here in Michigan, there are a few cops who actually have a tool to measure the tinting on a car. Since our state requires a doctor's script to actually allow the tinting to be on the car, they have been checking some who have ultra dark tint on their windows to see if it is even legal.
my windows are already at 30 percent. my car windows are at 22 percent. yes, i have a access to a light meter. buddy owns a shop and it's a required tool in order for the shop to be certified by the state to do safety inspections. windows already come with tint. so, to find something to not exceed that 30 percent. is going to be very hard. roll down your window and look through it. then above it. you'll see the difference in lighting.