Big Ben's Panorama Tutorials

Determining the Nodal Point of a Lens

Determining the nodal point of a lens is quite easy to do visually.  You will need two vertical features to use as reference points e.g. a doorway, flag/light pole, corner of a all etc...  One must be very close to the camera, the other, far away.  You will also need an adjustable tripod pano head or a focussing rail to adjust the position of the camera relative to the axis of rotation. Accuracy will be in the order of 1mm for a circular fisheye lens.  Accuracy will be greater with the near object as close to the camera as possible.

The diagram below shows what happens in the three possible situations.  Note that the relative positions of the objects on each side of the gap is determined from the nodal point of the lens, not the axis of rotation.

Legend
Rotation axis	Camera & nodal point
Rotation axis at nodal point
	Gap remains constant
Rotation axis forward of nodal point
	Rotating camera away from near object increases gap width Rotating camera towards near object reduces gap width
Rotation axis behind of nodal point
	Rotating camera away from near object reduces gap width Rotating camera towards near object increases gap width