auto black card 
auto white card
manual black card 
manual white card
For the white surface I used paper, for the black surface I used a plastic box. The auto settings had similar ISO and shutter speed. By increasing the ISO and decreasing shutter speed the white paper lightened up. By decreasing the ISO and increasing shutter speed, the black box got darker.
Better to use exposure compensation in shooting photographs. But good results. You can have problems with noise and/or slow shutter with your method