On a tele zoom lens can the nodal point be almost beyond the camera?

[Early Riser]

Here's something I have never encountered before. I just tested all my lenses for their nodal point using the traditional method of aligning two objects and differing distances and then swinging the camera back and forth to find the spot where the perspective between the two is constant. No problems or surprises with all my lenses except the 70-200mm Nikkor G f2.8 VRII. At 70mm that nodal point seemed reasonably placed as compared to my non zoom lenses although the camera body was much closer to the pivot point than with the other lenses. But as I zoomed to different focal lengths the camera moved more and more forward, that is until at 200mm it appears that the nodal point is somehow behind the lens and nearly behind the camera!!

I tried this with a variety of subjects the furthest close object being maybe 40-50 feet away and then aligning it with infinity objects. And every test confirmed that the nodal point is behind the camera body, or damn close to that, because that's the only point where the near and far objects maintain their relative perspective, all other positions just make the perspectives change. I know the 70-200 VRII has some strange optical qualities like it's not really a 200mm when you are working at less than infinity, but this is just bizarre. Is this even possible???

 

[John Koehrer]

Claiming total ignorance of the question, here's a (sort of) expansion: Does the nodal point change as the fl is
changed with a zoom lens?

I know that with a LF tele the extension is shorter than the fl.

 

[Early Riser]

Claiming total ignorance of the question, here's a (sort of) expansion: Does the nodal point change as the fl is
changed with a zoom lens?

I know that with a LF tele the extension is shorter than the fl.

Yes the nodal point does change significantly with this lens as the FL changes. And as test I also tried my 300mm f4PF nikkor and it's nodal point is ALSO behind the camera. And further when you stop down the aperture and shine a light into the 300mm, the diaphragm blades look like they are BEHIND the camera, that is if one were to judge where the aperture is located it actually looks like it's inches behind the camera body. I guess this is an effect of it being a telephoto design.

 

[MattKing]

Correct me if I am wrong, but having the nodal point outside and behind the lens elements is part of the definition of a telephoto lens.

 

[Early Riser]

Correct me if I am wrong, but having the nodal point outside and behind the lens elements is part of the definition of a telephoto lens.

Matt I have no idea. It's just really weird that the 70-200 nikkor and the 300 nikkor are inches infront of the pivot point. Then again I have never checked for a nodal point on a lens longer than 135mm.

 

[bernard_L]

Once again, the point around which the camera must rotate to ensure seamless panoramas for near and distant objects is the (center of the) entrance pupil, not the nodal point. And... the entrance pupil is not the rim of the front lens.

Possibly the commercial name Nodal Ninja has contributed to entrench that error. Another example of the interweb propagating confusion and error.

Something else. There is nothing weird with the entrance pupil being outside the physical lens. There is a class of lenses, called telecentric, where the entrance pupil is at infinity (in front or behind, it's the same); this is to eliminate certain errors when a camera is used to measure X-Y positions in "machine vision".

 

[Marco Gilardetti]

Possibly the commercial name Nodal Ninja has contributed to entrench that error. Another example of the interweb propagating confusion and error.

I don't think so. I believe it descends from the fact that classic swing-lens cameras have the lens revolving on the nodal point. However, in these cameras the film is not "flat" but wrapped around a cylinder, and the lens/aperture will not change distance in relation to the film as it is generally a fixed focus. Hence, I believe, the common over-inference that also with standard cameras the nodal point can be used for panoramas, stitching and alike.

 

[Nodda Duma]

The answer to the original question is yes.

However, Bernard is correct. The point of rotation to avoid parallax in a panoramic is the entrance pupil which is not the same as the front node. Not that it makes a practical difference. Your experiment will find the correct point of rotation regardless of what anyone thinks that point is called.

-Jason