Is Green screen (background) okay for studio portrait shot?
two or three king size sheets is all you need and expose the sheets 1/2 to 1 stop over the people. do not go above that. if it is a bit gray then you can just use the dodge tool set to highlights to make it pure white. A lot fasteer to do it in st that worry about a perfectly lit back drop. keep 6 ft to 10 feet between the background and the group to prevent flare and shadows.