In the studio photographs shown above, do you see the ghostly shape of another human being behind the baby- but hidden by a drape or curtain?
The January 2010 issue of The Paper and Advertising Collectors Marketplace (PAC CM) had an interesting article on "Uncovering the Hidden Mother (and Father) in Photographs. In the nineteenth century, exposure times for photographs were often measured by several seconds rather than fractions of a second as in modern cameras. So, how does a photographer hold a squirming baby down long enough to take an un-blurred picture- and still focus mainly on the baby? One way is to have the mother sit in a chair, hold the baby, and cover the mother's face with a drape or curtain.
The PAC CM magazine article mentioned several other techniques. In some cases, holes in the back of the chair were large enough for the mother to squat down and reach through the holes to hold the baby. A photographer named Fred Pohle invented a medal holder which babies were strapped into and held motionless for the photographer. Perhaps a less traumatic method was for the mother to hold the baby and then be cropped out of the picture during the processing or matting the picture so that the mother was hidden in the frame of the mounted photograph.
The article prompted me to go through my own photo collection looking for vintage baby pictures of my family to see if any of these techniques were used- particularly "Hidden mothers".