Green screen

I hope this is the right place to post this. What would be the disadvantage of shooting portraits using a green screen and then adding whatever backdrop color in post editing? It seems this could be a good way to have different backdrop looks without having multiple backdrops.

One major problem is if the subject is wearing anything with green on it, because that'll be replaced and the background will show through.

The weatherman on TV wore a green tie one night, that was funny. And a few weeks ago a group of friends and I had our picture taken in front of a green screen, and my friend in a green shirt had her body replaced with a bookshelf.

Plus the subject and background never really seem to go together in my opinion.

If you don't get the lighting just right you can get a tint from the screen on your subject. If its well done, and you don't mind the PP work it should work out alright.

One year the photographer doing my kids' school picture used this technique, and not well IMHO. There was terrible haloing(?) around the kids and they seemed to "float" in front of the background.

Done well I imagine this could be a time saving alternative to changing backdrops. Done poorly and it's painfully obvious.