When the lenses are separated by less than 2.5". This is common in macro, or closeup work.

Use of a shorter than normal stereo base in order to reduce depth distortion in portraiture and close-up stereography; it produces an effect known as Giantism (qv). The converse of hyperstereo.

Using a baseline that is less than the distance between the left and right eyes when taking the pictures. This exaggerates the size of the objects, making them look larger than life. A good use for this would be 3D photographs of small objects- one could make a train set look life size.