70-200mm f2.8 vrII pano question

[DavidG]

Hi All,

I got a panoramic rail today and started testing for the nodal points (entrance pupil for those who prefer that term

On the 70-200mm f2.8 lens it appears to be in the area where the lenses gold lettering is. This surprised me as I thought it would have been much closer to where the lens mounts the body.

Is this similar to your experiences?

David

[arthurking83]

The question is kind of pointless in one respect.

What focal length?

Without knowing what focal length you are after, it's harder to find a definitive point for the entrance pupil.

Being a zoom lens, it's almost certain to change with the varying focal lengths of the lens.

From what I can see:

using this diagram as the basis of where the lens optics lie.
Immediately behind the front three ED lens elements, is a group of four element that appear to be the entrance pupil(or more importantly the image forming rays).
With the lens pictured as per the Nikon diagram, the lens looks to be at 70mm. Those four(or five) lenses appear to coincide with the focus ring.

On a diagram that Ive seen, that lens group moves back as you zoom to 200mm, where the group then corresponds with the gold lettering.

[Tommo1965]

you have both lost me ...

[Epoc]

This is different depending on how the lens is built. The Tokina 10-17mm does not change while some other zoom lenses may change. Eg. The 15-30mm Sigma which changes from 120 to 134mm. You have to test it. Once your close, it doesn't take much time to adjust it.

Here's a great page by a very knowledgeable panorama chap, on the whole nodal/entrance/no parallax point.

http://www.johnhpanos.com/epcalib.htm

[ameerat42]

Interesting, Epoc. Ta, Am.

[arthurking83]

The link to the lens database is handy(now bookmarked) .. but unfortunately doesn't cover either of Nikon's 70-200/2.8's. The 70-200/4 VR is listed and has the entrance pupils listed there for 70 and 200mm, but don't rely on those values for the 70-200/2.8. Both lenses will most likely be different, as they have different optical designs.

[DavidG]

Thanks to all, I can find "the point" but was just interested in your experiences.

Cheers,

David