Pictures gallery from the film:    Darby O'Gill and the Little People (1959)

Page 2.
 
 
 
 

At that time, Peter Ellenshaw had two matte artists helping him at Disney. Albert Whitlock and Jim Fetherolf.
One of the paintings on which Albert Whitlock collaborated was  the one with the giant wheel.
 

(left)The set with the  oversized elements. (right) The undesired elements matted out, ready for the painting.

The final shot with the painting composed.

Two behind the scene pictures, showing how the false perspective effects were filmed.

The figure  in red was at the foreground, close to the camera, the blue one was far away.
Taking care of matching the same lightening, the effect of two differente scales worked pretty well.

At this picture you can see the actor on the foreground, pretending that he his talking with the small one, who is far away of camera.

 

Some samples of the false perspective trick.