When growing cannabis, does the dark in the light-dark cycle need to be absoultely pitch dark, or would dark ish be ok too?

I was told that the dark cycle should be as dark as the outside would be at night.

When growing in a greenhouse/outside that is as dark as it ever gets.

Not a big deal in vegetative growth stage. Flowering is a different story. I had three plants in my tent, there was a small light leak that I didn't notice right away. The one closest to the leak didn't flower but the other two did. Absolute pitch black is not required, but there is a point that's too much. Led indicators on powerbars or fans generally aren't a problem. If light is an issue, grow auto flower.

Dark, yip, ideal, you can achieve it easily with tents or cubbards

Black out dark.