35mm FF body:
a 105mm lens gives between 4-6ft working distance for a 15" headshot, and about 7ft working distance for a 24" head and shoulders shot.
A 135mm lens gives 5-9ft working distance for a 15" headshot and 9ft working distance for a 24" head and shoulder shot.
A 85mm lens is not recommended for anything less that half-body shots.