The Ames Room IllusionImage courtesy Mosso
The image above was captured by a visitor to the "Ames room" in Vilette science museum in Paris, France and uploaded to Flickr, a photo-sharing website. In the room, the individual on the left appears to be very tall, while the person on the right looks very small. In reality, both people are of approximately the same height and size.
The effect works by utilizing a distorted room to create the illusion of a dramatic disparity in size. While the room appears square-shaped from the viewers perspective, it is actually has a trapezoidal shape. The woman on the right hand side of the image above is actually standing in a corner that is much further away than the woman on the left.
The illusion leads the viewer to believe that the two individuals are standing in the same depth of field, when in reality the subject is standing much closer. The woman on the left in the image above appears at a much greater visual angle, but the fact that she appears to be at the same depth of field as the figure on the right makes the closer individual look much larger.
The effect can be observed in a number of films, including The Lord of the Rings trilogy. Note the early scenes in The Fellowship of the Ring where the effect is prominently used to make Gandalf appear larger than the hobbits.
You can see more examples of Ames rooms in these YouTube videos.
Ryan, C. (1997). Exploring Perception. Brooks/Cole Publishing: Pacific Grove, CA.