720 panorama Shanghai, flash panorama, 3d panorama, 720 photography Shanghai
Determining the Nodal Point of a Lens
While it is not entirely essential to accurately position your camera for each image, it does make things a LOT easier if the lens is rotated as close as possible around its nodal point. By doing so, you remove parallax errors which may require a lot of retouching to make things look right in the finished panorama.
Determining the nodal point of a lens is quite easy to do visually. You will need two vertical features to use as reference points e.g. a doorway, flag/light pole, corner of a all etc... One must be very close to the camera, the other, far away. You will also need an adjustable tripod pano head or a focussing rail to adjust the position of the camera relative to the axis of rotation. Accuracy will be in the order of 1mm for a circular fisheye lens. Accuracy will be greater with the near object as close to the camera as possible.
The diagram below shows what happens in the three possible situations. Note that the relative positions of the objects on each side of the gap is determined from the nodal point of the lens, not the axis of rotation.
Legend
Rotation axis
Camera & nodal point
Rotation axis at nodal point
For years, I have been using for panoramic shootings a 303-Plus (+) head. I have decided to switch to a 303-SPH which is a very good choice to expand its use to Quicktime VR 720°/180° shootings. After a few days of use and tests (with all due respect for its manufacturing and design quality), a few issues appeared :
Inaccuracy of the swing system : the system only holds marks for each degree to align by hand in front of a spot but there is no blocking mark. Reproducing 2 (or more) identical views is therefore impossible once the swing position has been changed. => replace by a thinner horizontal 300N or MA300.
