What I’m wondering is how pitch dark you have to be?
I have a meter that read 0 lux and when I took a picture at 60s long exposure along with 400 iso I got this:
But I edited it (adjust exposure to full and some other things like contrast, shadows, brightness etc) and I got this:
It’s a custom box I’m building and have been fighting it all day.
Am wondering if what you all think if it’s good enough it really needs to be a true 0 light pitch dark where even editing it I can’t see anything?
If it is dark in the room where you box is during lights off time you are fine.
As for using light meter in the dark in useless, I thought I read that a full moon on a clear night is like a 1 lux. Meaning your eyes are more sensitive to light than the meters.
If you want to know for sure absolutely no light leaks then put a light inside the box, close it up and turn out the lights in the room wait and see.
Hah honestly I guess that true about the light outside of the tent… at some points (in the basement) it may not be totally pitch dark but it will usually be mostly dark, so that in combo with what I got I hope will be good enough?
I have some leaks on the outside of my tent ican see, but I’m in a finished outbuilding. The only problems from light was my own stupidity. I put in a new space heater on a sensor, did not check to see if there were any lights on it, and it was set for my night time temps so I never saw it running. Realized it when I had a plant hermie and tried to figure out why.
That sucks, sorry to hear it
That’s my 2nd light test. I first, turn all the room lighting on, get inside the dark tent, and check for leaks and fix them (if found). Then test from outside as @OGBohab suggested. Wasted effort, IDK.
When you get in and check are you just using your eyes?
Yes, I wasn’t born with light meters, JK. After my eyes adjust to the dark, I’ll see any obvious leaks, like around zipper flaps. The flap prevents light from getting out. But a bad zipper can pass light and reflect it to the sides, inside. I’d see a dark grey area on the mylar, which should be black. Since I retired, lights are on 0900 - 2100 hrs. and leaks are not a concern.
If you can get in the space while closed, and cant see any light, you are good.
I would suggest using genetics from reputable breeders that actually test their shit. Any breeder / seedmaker in this day and age that is worth a damn, stress tests the shit out of their plants, which includes giving them light leaks that would probably surprise you.
I would almost put my weeks pay to say that shitty genetics cause far more problems than any minor light leak ever would.
Reason I was asking is because if I’m shooting a pic at a 60 sec exposure at 400 iso, and it comes out black before editing, I doubt I’m seeing that with my eyes because I know from Astro photography it brings out stars I can’t see
Any chance there’s an LED (i.e. power indicator) on the camera & that’s whats being picked up in the photo? Interesting pics but am confident after abusing plants that unless the genes are weak you can expose them to more than you’d think. The only real problem I’ve had was outdoor with urban light pollution 
This is good to hear as further confirmation, *it was just one guy that got me worried…
There was no LED in the pictures.
I think I will be fine, but some of you may possibly see as I think I will eventually do a journal
You’re good! Probably mor light tight than any of my rooms. 
I have a bad zipper on my flower tent,happened about a month ago, still waiting to see if anything herms
If it’s too dark for you to read a newspaper, then it’s dark enough for flowering. This information has been thoroughly tested and it’s definitely true. Rays of light hitting plants could probably cause some issues…
I had a plant in my garden that budded on all branches except one that was hit by a light from my porch. Weird. If I hadn’t seen it with my own eyes I wouldn’t have believed it could happen. Once I tied the branch down below some vegetation that would block the light, it started to Bud
I think that having it too perfectly dark could actually be detrimental, especially if you are trying to make any selections make seeds or breed lines. The closer to a “perfect” or completely controlled environment you get, the less resistant to stresses or changes in environment that the the plants you select for will ultimately have over generations, even if you are just making and saving seed for your next crop. Doesn’t mean it’s not worth the time and effort to try and make it nice for them, just possibly detrimental to go over the top with it.
Just my 2cents.
The theory of it never being truly dark outside holds true but you sure don’t want a pencil beam of bright light coming in. The things to look for when all the equipment is inside are the small lights on remote sensors and sometimes on ballasts or things like that.
Thanks everyone, I really appreciate all of your input, makes me def feel rest assured! 
Another update, this is what my fucked up box looks like with the lights on from the outside, guess I should have put more coats on it lol:
Those two are also with the outside light off I just used my camera flash, the funny thing is when the normal outside lights are on, the box looks completely black on the outside.
This pic was with no camera flash.
