« Great Photography... | Main | TIME FOR A MIRRORLES... »

Where are the No Parallax Points for some Canon Ef-M Lens?

Those who capture photographic panoramas need to know the No Parallax Points (NPPs) for their lenses. The NPP is often referred to as a nodal point, but that is a misnomer. In fact, every lens has two nodal points, and neither is relevant to this discussion. The proper rotation axis for a panoramic photograph lies in the entrance pupil of the lens. If one rotates the camera around this axis when taking photographs, then the images can be stitched together accurately so that even close-up objects will be properly represented.

Now I come to the crux of the matter. I have a Canon EF-M mount lens, and I need to locate the relevant NPPs. If one is lucky, the NPPs can be found online. Some lenses appear in the Nodal Ninja or Panotools sites. However, I could not find the NPPs for my EF-M lens online. The only recourse was for me to determine the NPPs for myself. The crudest determination is to look into the front of the unmounted lens to see where the entrance pupil appears to be. About the only thing this procedure reveals is that the NPP is close to the front of a zoom lens at wide angle settings and that it recedes as the lens is zoomed to longer focal lengths. The measurement of the NPP requires something more precise.

There is no shortage of advice about how to determine NPPs online. For example this video describes the operation. Basically the rotation axis must be chosen so that near by objects and distant objects will maintain their relative positions in the image as the camera is rotated. This is a bit more difficult than it might appear. Fortunately, I have a Nodal Ninja 3 tripod head, which makes this operation relatively easy.

In this measurement the camera is held in the vertical (portrait) position, and the image can be viewed through the EVF or on the LCD with 10x magnification. I rotated the camera about the horizontal axe and used rulers placed at 3’ and 14’ from the lens. This is a trial and error measurement made by sliding the camera back and forth on a rail, and I think the results are accurate to about 10%. Here is the pdf file: Table of NPP valuesIf you find discrepancies, please let me know.

You will find that fairly accurate NPPs are important when nearby objects appear in an image. When everything is far away, handheld rotation will work for panoramas.


Post a Comment:
  • HTML Syntax: NOT allowed

« Great Photography... | Main | TIME FOR A MIRRORLES... »