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‌Coefficient Escalation for Refining Solves

As you begin to solve your anamorphic shot, usually you’ll do an initial solve with only simpler distortion features enabled. You might want to consider using “Always slow” mode on the Advanced Solver Settings page, especially if you have several nearly-redundant distortion coefficients enabled.

Then, you’ll refine the solve by turning on additional terms to reduce the error — but only keeping terms that make a significant contribution to reducing the error.

Tip: Use ‘File/Export/Lens/Solver Distortion as Script’ to write out the distortion results from the solver for use in other shots from the same camera setup. Use Script/Run Script to run it later.

You’ll need to decide which distortion features to turn on, and at what time in your process to do so. This is an experiential skill, considering the shots you are handling.

Don’t turn on ROT (rotation) to start; it can’t be determined unless the distortion depends on the alignment, ie there are different distortion parameters in CX** and CY**, parameters other than C*02, C*22, and C*06 are nonzero, or VSCL isn’t 1. HSCL and VSCL should be left for later lens breathing analysis.

You might start with C*02, C*22, and C*04, then maybe add C*24, C*44, and C*06. Consider adding ROT, HCTR, and VCTR. Continue to C*26, C*46, and C*66 only if the situation warrants it (probably worth at least checking anamorphic distance before that0.

Tip: Solve for distortion during slower-moving parts of the shot; keep distortion unchanged during rapid slews. Rolling shutter plus anamorphic distortion equals one big mess. Using key-at-frame mode, don’t put keys in the middle of rapid slews.

With lidar scans, if you have many locked trackers, you can go directly to solving many parameters, including anamorphic distance, and this is likely better than doing it in stages. You might leave only the asymmetric 6 th-order terms unsolved to start.

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