Total black is simply insurance. Think about it. Outside you've got all kinds of night lights and plants do fine on their own . . . and then there's the moon.
AS DARK AS YOU CAN GET IT SHOULD BE FINE.
I do total black until flowers established, then don't worry so much about a little bit of light now and then. NO hermies here.
I also stapled a dark sheet up in front of my intake fan, which waves in the breeze while shading the light even more.