Most higher-end image editing programs now feature automated panorama stitching, but if you don't rotate the lens on its nodal point while capturing the individual images for your spherical panorama, even the best image editing programs will find it challenging to stitch all of the images perfectly. Instead, portions of the stitched areas don't precisely line up, a result of parallax errors. Rotating the lens on its nodal point allows you to avoid those parallax errors, ultimately leading to a better panoramic image.
But how do you find the nodal point for your lens? The solution is probably easier than you think. Yesterday I determined the nodal points for eight lenses (one at two different focal lengths) using my pano rig.
To find your lens' nodal point:
1. Set up your camera along with aligned subjects.
Set up your tripod-mounted pano rig so that it is level and pointed at two objects that are perfectly lined up in the center of your viewfinder/frame using Live View at max magnification. For me, that was two light stands set up in my studio about 6' (1.83m) apart. The farthest light stand was extended just a little bit higher than the closest light stand to make aligning the two subjects easier.
2. Rotate the camera left or right and move the camera forward/backward to create an identical view.
Move your magnified live view frame all the way to the left or right, then rotate the camera so that the front object is within the magnified view. Now, move the camera forward or backward using the nodal rail until the two objects are lined up just as they had been in the center of the frame view.
3. Record your results.
Record the position of the nodal rail in your clamp, such as "Clamp centered on 49mm rail mark," the lens being used and (if using a zoom lens) the focal length setting of the lens. If using a zoom lens for your panos, you'll need to determine the nodal points for all focal lengths you intend on using for your panos. Typically speaking, I usually calculate the nodal points for the shortest and longest focal lengths of a zoom lens. I find it handy to record the measurements in a cloud-based document so that they can be accessed from any location where data services can be accessed. Also, keep in mind that your nodal point calculations may be different depending on whether your camera is in portrait orientation or landscape orientation. Typically, you'll want to orient your camera vertically to maximize your panorama's resolution. However, if shooting horizontally, the plates in your L-brackets may be offset from one another. For 5D Mark III L-bracket, the offset is 15.5mm, meaning I have to subtract 15.5mm from my vertical orientation measurement to get the landscape oriented one. If planning to travel to remote areas to capture panoramic images, storing the nodal point measurement values locally on your smartphone in a notepad app (or alternately in a traditional paper notepad) would be best.
My particular pano rig consists of a bidirectional clamp and a multi-purpose rail. Instead of moving the rail in the tripod's head, I move the bidirectional clamp that's connected to the camera. Therefore, I have to ensure that the rail is clamped into the index rotator's clamp at the exact same position each time if I ever entirely break down the setup. While that sounds a bit complicated, it's not in practice. I just make sure the first measurement mark on the rail is lined up with the front edge of the index rotator clamp, and all is well.
After calculating the nodal points for several of my lenses, I got the itch to create another 360-degree panorama. After a short time thinking about the possible locations to photograph, as you can see from above, our renovated second bedroom was the subject I chose. To capture the image, I used a Canon EOS 5D Mark III and Rokinon 14mm f/2.8 lens a 3-shot exposure bracket at each 20° interval. I then combined the exposure brackets in Lightroom (using identical settings for each HDR blend) and compiled the panoramic image with Hugin.