First off their is no other black parts, just darker pixels and we know it was photoshop, no one will judge you if you just say it, but don't lie and say it isn't.
What color would you say is the thing to the right of the sign which appears to be the floor?
I'm not lying. I didn't photoshop and I know the model doesn't have the skills to do it. She takes sign pics all the time so there's no reason for her to photoshop it.
No there isn't any big dark area, and you can't not lie about the analysis of the picture because you can test the image your self they all show the same thing. That area is very dark and it is one part. It isn't the RGB colors which shows it is was digitally altered.
I also know cammodels and most of them are handy with photoshop it is part their job to touch up and focus things on them.
Maybe touched up? No something was deleted and then something was added from another image or created on top of it. Trust me I know these things