If you are thinking of purchasing a spherical head, this is what you need to consider.
This is a modified 4 year old Nodal Ninja 4 that is no longer in production.
A. 3 point level.
Always an Option. The stitching software doesn’t know where level is. This sets level and reduces the chance of a skewed panorama. It’s difficult and time consuming to level the panorama afterwards. A tripod can be used instead of. However, it’s more difficult and not as accurate. Because of the weight it is not recommended to use the head that’s already on the tripod or a half ball type swivel.
B. Rotator.
3/8-16 tripod connection. It rotates 360 horizontally. It has detents to set the number of images.
C. Horizontal Rail.
Used to calibrate the camera’s center of rotation.
D. Nadir Adaptor.
Used to photograph the ground below by swiveling the vertical rail assembly 180. Look for a head with it included.
E.Vertical Rail Assembly.
Rotate the camera vertically. Pictured is the head in the 0 (horizontal) position. Is where the parallax adjustment is made.
F. Quick Disconnect.
Optional. Mating the camera to the head can sometimes be tricky. The camera needs to be flush with the head. One solution might be adding a quick disconnect without needing to make any modifications (drilling, filing, etc).
G. Camera & Lens.
Make sure the head can handle the weight.
At present I'm trying out a tripod that should make taking the nadir easier.
Feel free to contact me about any head you are thinking of getting. Even if it doesn’t have all the parts, sometimes they can be added afterwards.
NOTE: There are 2 types of tripod threads. Most used today is the ¼-20 thread. There is also a much stronger thread known as a 3/8-16. An adaptor/insert is used to fit a female 3/8-16 thread to a male 1/4 -20. Many times these inserts are included with the item. However, the only way a 3/8-16 male thread can be made to fit a female ¼-20 is by drilling and tapping. If you need me to drill and tap the hole to a larger size, send me an image of it first. Most likely I’ll be able to do it.