Nodal point of a 17-40?

Hey guys I was browsing around on the reallyrightstuff.com website and read some interesting things about panoramic photography. In a short write up they mentions lens Nodal Points…

I know this point varies from lens to lens and was curious to see if anyone knew what the Nodal Point of a 17-40 lens is?

I’ve been searching around on the internet and I’m not sure if anyone keeps a listing of this obscure spec. Ive found a complete listing for Nikon lenses but have not seen anything for Canons…

Thanks a ton guys...

i forgot to add one other thing... i know the Nodal point will change depending on what focal length you set but i was hoping someone had specs on say the 17mm and/or the 40mm end...

Why?

To make use of the nodal point, you'll need a method of precisely centering the camera over it. It's probably easier to get a macro focussing rail and trial-and-error it for your camera and lens. To calculate it, you'd need to know all the specifics about the different elements and lens groups that make up the lens, and do some light-ray tracing calculations, or find it by experimentation. Canon hasn't published it.

I guess I would contact Canon and ask them.

To phrase it differently, I would say that the nodal point is important if you are trying to do wide panoramics. The regular tripod hole on the bottom of your camera body is typically not correct. Sometimes the nodal point in in the center of the lens, and sometimes it is as far back as inside the lens mount. You ought to be able to figure this out by experiment.

---Bob Gross---

It's probably less important if these are going to be digitally stitched together. Photoshop does make it very easy to fix together slightly offset photos. I've taken several panoramas handheld and joined them with little effort. The only key thing is remembering to switch the camera to manual.

http://www.kaidan.com/​nodalpoint.html