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Nodal Tripod-Mode Shots
In a tripod-mode shot (also known as a nodal pan in technical terms), the camera pans, tilts, rolls, perhaps zooms—but does not translate. No 3-D range information can be extracted. That is both a limitation and a benefit: without a depth, these shots are the domain of traditional 2-D compositing, amenable to a variety of tricks and gimmicks such as the “Honey, I Shrunk the Kids” effect.
In the "old days," effects shots used a camera on a tripod so that elements could be composited in without the need for 3D analysis: at most a simple four-corner pinning. No true 3D information was available or necessary.
Now, although SynthEyes is designed to handle shots where the camera translates, producing full 3D information, shots still come in that only have pan, tilt, roll, and maybe zoom... and of course we still need to do a 3D insert into them.
You should always be on the lookout for tripod shots, even when you are told "was shot on a crane," "was shot hand-held", etc. Unless the camera translates, there's no 3D. If everything is far away on the horizon, your 6 feet of camera motion doesn't amount to much either.
Fortunately you can easily learn to recognize these shots. It can be simpler to learn if you first run an auto-track, then you turn off the image display in the camera viewport, and just watch the movement of the trackers—that's all you need, and all SynthEyes "sees." If the trackers all move together as a unit, it is a tripod shot. If they move around differently, it is not (discount any on actors or other moving objects; they should be deleted).
SynthEyes solves tripod shots for (only) the pan, tilt, and roll (optionally zoom) using the Tripod solving mode . And it helps you orient the tripod-solve scene into a 3-D workspace.
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