Why is the Nodal point important? – Les Ludgate

Nikon 1“The nodal points are widely misunderstood in photography, where it is commonly asserted that the light rays “intersect” at “the nodal point”, that the iris diaphragm of the lens is located there, and that this is the correct pivot point for panoramic photography, so as to avoid parallax error. ……….. A better choice of the point about which to pivot …..is the centre of the system’s entrance pupil.”  Wikipedia

So the photographers and the physicists argue over semantics.  Strictly speaking it’s not the nodal point but the centre of the lens pupil that’s important.  The concept however still holds true.  When taking pictures for a panorama you need to rotate the camera around a rotation point within the camera lens. Failing to do this may result in problems due to Parallax during the stitching process. Parallax is the apparent shifting of foreground objects relative to background objects when you change your point of view position.

The rotation point is usually about half way between the lens front element and the film plane. Mostly a point slightly in front of the camera body.

There is a lot of information on the net re finding the “Nodal point” and buying or making a bracket to achieve good results. Just type into your browser “Finding the nodal point “and read or watch video on the subject.

Other tips to making good panoramas include, overlapping images by a generous amount (1/3) and keeping the horizon level.  Set the exposure lock at the centre of interest in the panorama to aid in blending images.   Panoramas are difficult with very wide angle lenses (> 28mm) as the edges exhibit distortion making it hard to match.  Using a longer lens and taking vertical shots in a horizontal panorama can give the extra coverage you need so that the wider angle lens should not be necessary.

I have made a simple bracket from an old Metz flash head to try and achieve the desired positioning of the camera and lens. (picture above) The Metz bracket has a slot milled in it and allows the camera to be positioned over the rotating tripod head. You need to be able to centre the camera over the tripod head and then be able to move the camera forwards along the slot and using information from the web you will be able to achieve the desired rotation position. What photographers call ”the nodal point”

Nodal point

The nodal point is a point within the lens where a light ray passing through the centre appears to have crossed the midline.    There are two points, one for the front surface and one for the back.

Entrance Pupil

A better choice of the point about which to pivot …..is the centre of the system’s entrance pupil

 

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