If you use zoom lenses, a lens' optical center (frequently and incorrectly referred to as the nodal point) changes for each focal setting. This means you'll need to calibrate for all frequently used settings. With my Canon 10-22, I have nodal slide settings for 10, 17, and 22mm. Oddly, the 10mm position is in between those for 17 and 22.
A post-it tape chart is attached directly to the slide to look up often-used settings. These figures include the focal length, its nodal slide position, how many degrees to swing the upper rig for proper shot overlap and the number of shots I'll need for a full 360º pano if I decide that's what I want.
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