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Strategies for Animated Parameters
When readying to solve a shot, you should examine whether it appears to have a zoom or focus breathing (possibly by pulling the focus metadata into the graph editor using the ‘Load focus channel from metadata’ script or the “File/Import/Metadata/Import focus channel from YAML” importer if you have YAML metadata). If neither zoom nor focus breathing is present, you can stick with strictly non-animated parameters, ie just Calculate mode.
Tip: Continue to be aware of the possibility of a hidden zoom once you’ve solved the shot, manifested by the camera seeming to unexpectedly push in or pull back. Hidden zooms are fairly common on integrated “camcorders” with a handy zoom button.
If the change requiring animated distortion parameters is relatively small, you should likely start by getting a successful solve with the relevant parameters set to Calculate, and Refine the solve with the animated parameters after that. Getting an initial solve with significant animated parameters may be difficult, requiring many trackers. Locking the solve to a lidar scan will improve the stability, though many trackers will still be necessary for complex anamorphic shots.
To solve your shot using animated lens parameters, you may be tempted to use the Animate by frame option exclusively. It sounds great, yay, we’ll get as much data as possible, but in practice it guarantees that you’ll get as much noise and jitter as possible, even if you add lots more trackers per frame. It can unstabilize the solve, making an otherwise solvable shot unsolvable. This isn’t a software issue, it’s fundamental mathematics (and even quantum mechanics).
Instead, using the Animate at keys option is your path to a successful usable solve. You will place keys throughout the shot at significant frames where the distortion values changing. As with other animated tracks, the distortion values will be interpolated between the key frames. During the solve, SynthEyes’s advanced solver will optimize the solve to produce the best solution not only on the key frames, but the best solution for all the frames, taking the linear interpolation into account. It’s a nifty trick, but it does require that only linear interpolation can be used.
You can use any available information to decide where to place the key frames on the animated track, for example, by carefully examining the shot, by looking at the solved lens zoom track, by looking at a lens focus track, as retrieved from the metadata or…
You can also use the Animate by frame option to get a frame-by-frame solve for any animated parameter, typically a low order distortion parameter that changes significantly, or the vertical scale for anamorphic shots with focus breathing. (You’ll need to clear the track before placing keys.)
Based on any of these data sources, you’ll select the Animate at keys option for the desired parameters, then place keyframes on them at the desired frames. The
+Keys button on the control panel will help with that, since it places keys on the current frame of all parameters that are in Animate at keys mode.
You can use the Script/Lens/Add distortion keys script to add keys a certain number of frames apart over the current playback range; you can manipulate the playback range as you run the script repeatedly if necessary.
In areas where a focus or zoom change is first ramping up to speed, you might put 2-3 keys spaced several frames apart. Resist the temptation to add many keys, as that will just make you want to edit them later. You can put a key at the beginning and end of static (for the lens) periods of the shot, maybe with one or two in the middle as a cross-check for longer sections.
The result of Animate at keys solves should be nice clean solves that still accurately track the changing situation.
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