Lens Center. Where is it?
I use to have a coopix. When panoweaver 4 came out the seam problems went away. In fact panoweaver 4 and 5 are almost bullet proof when using 3 fisheyes from a coolpix. I am now using a 20D and Sigma 8 F3.5 with a KingPano rotator taking 4 shot for a Drum. The rotator is perfect level; the camera lens is perfect horizontal level. The lens from left to right is exactly over the center of rotation.
I have very noticeable seems problems. Especially shows up with wood blanked ceilings.
The only thing it could be is the lens from front to back centered position over the center of rotation. Where is the center of the Sigma Lens? I have it about 3/8" back from the front of the lens. It looks to me like the center of little round glass ball in the lens would be center nodal point. But I am not sure and have not had any luck Googling up the answer.