Probably correct. When shooting only two shots around, the images join at 90 degrees to the lens axis, so the entrance pupil must be visible when looking from the side of the lens in a direction at right angles to the lens axis. The entrance pupil is the point about which you need to rotate the lens, which will be well forward of the gold ring. See the photo at the end of this tutorial: http://www.johnhpanos.com/epcalib.html.
Originally Posted by CAMdigital