Light is light, and too much of it can cause issues with photoperiod plants. If you go outside on a full moon night, you can see a little after your eyes get used to the darkness, but compared to a streetlight, it is pretty dim... too dim to really affect plants, although some might be more affected than others. As mentioned, our eyes are pretty sensitive to light. I would consider my photoperiod with the times representing the sunrise/sunset for your location. Around here, I'd consider the sunrise/light period starting around 6 am and ending around 8:30pm. Even though it is only considered about 14-15 hrs of daylight, the plants outside don't usually switch to flowering until mid August. It seems to take a decreasing photoperiod to trigger flowering if you don't go the whole way to 12/12 for flowering, otherwise the plants wouldn't stay in veg mode too long...at least around here!