Usually, it was arranged so that sitters leaned their elbows on a support such as a posing table, the height of which could be adjusted, or else head rests were used that did not show in the picture, and this led to most daguerreotype portraits having stiff, lifeless poses. Some exceptions exist, with lively expressions full of character, as photographers saw the potential of the new medium, and would have used the tableau vivant technique. These are represented in museum collections and are the most sought after by private collectors today. In the case of young children, their mothers were sometimes hidden in the frame, to calm them and keep them still so as to prevent blurring.