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Preparatory Solves
For shots with a small focus pull, you should get an initial solve for the shot neglecting the focus change, then pin it down using the techniques described in following sections.
You’ll need a Lens Model that has a vertical scale (VSCL) parameter, either the anamorphic types or Radial+Squash model. Use an anamorphic type if the shot is anamorphic, or if you want to remove the focus zoom (to HSCL instead). Unless it’s an active anamorphic shot (lots of motion or locked to lidar), use one of the two Merged anamorphic models, as with little motion there won’t be enough information to compute separate X and Y distortion coefficients.
If a focus change causes major effects, you may need to solve initially as a zoom shot (and focus breathing really is a zoom). Or, you may be able to solve part of the shot first, then proceed into solving the section with the focus pull with SynthEyes set up to determine it. Solving for VSCL during an initial solve should be avoided if possible, as it can be nearly equivalent to a camera motion, and that ambiguity will destabilize the solve, unless the shot is locked to lidar data.
Tip: Commonly, rack focus shots are nearly stationary except for some hand-held sway, and as a result there is too little motion to determine the field of view or any lens distortion. You should solve such cameras with a Known field of view.
Tip #2: You should lock tripod shot’s rotation angles on the shot’s first frame (only!), normally to 0,0,0, so that repeated solves don’t cause the shot to wander.
Tip #: You’re going to need VSCL later, which is only available for anamorphic solves, but because there’s no distortion, use the Merged version.
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