Using a no parallax nodal point for accuracy in combining multiple images into a panoramic

In my blog post of two days ago I showed the panoramic image above comprised up of four separate photos and combined later in Photoshop. Although I did mention that the camera was on a tripod, I skirted the issue of setting up the camera in a non-parallax condition to rotate around its nodal point. My distance from the subject and the fact that the camera was parallel to the ground made this something of a non-issue. One blog reader did pick up on this, however, and posted the following comment:

"Did you use a a nodal slide with the 70-200 or is it necessary at these distances?"

I thought it might be interesting to answer this briefly here without diving in so deeply that I require a lot of illustrations and image samples. I will save that for a later blog post.

Briefly stated, when performing a very accurate stitch of panoramic images, it is important to have the camera-lens combo rotate around a specific point that has no parallax. There are devices on the market to mount on a tripod and adjust to achieve this non-parallax state. 

This is a link to one of the simplest Youtube explanations of how to find the no-parallax point of the camera/lens. There are many panoramic heads on the market to help achieve accuracy in alignment. 

So why didn't I use one for to take this photo? Because I knew through testing that the tripod mount ring on the Nikon 70-200mm f/4 zoom was located in a position that places the lens near enough to the nodal point to be accurate for practical purposes in combining panoramic images taken at a large distance. I was working at infinity and the differences were negligible. My lens-to-tripod mounting plate was long enough to allow the camera to move back and forward on the tripod head. This achieved pretty much a perfect positioning of the camera/lens combo at a point of no-parallax when rotating on the tripod to take the multiple exposures. 

Nodal rails come in varying sizes. With the camera mounted to the back clamp and the main rail mounted to the rotating tripod clamp, the nodal rail can slide back and forth until the camera is located properly to achieve the no-parallax panorama. 

What about if you want to use a different lens without a tripod ring to create a panoramic image?  For accuracy you can use a nodal rail to adjust the position of the camera/lens combo on top of the rotating tripod head.