How to quickly change background colour behind intricate object?

[Louis26595917cat9]

Hi Team, 

I am looking for a fast way to get from Picture A to Picture B in photoshop. Essentially just making all of the fuzzy black background a pitch black background. I am currently using paintbrush tool and manually 'painting' in lightroom but wonder if there is an easier/automatic way in photoshop?

Also, if there would be a way to make all of the gravel darker at once without impacting the rest of the image.

Cheers!

[c.pfaffenbichler]

Have you tried Select > Subject as a starting point yet? 

[c.pfaffenbichler]