Hi Laddieervin,
I have used in many workflows this grid: (or previous version of it)
https://www.ssontech.com/content/lensGrid.pdf
It is the grid that is used for SynthEyes. If you print it out, ask for a “text print out” instead of a “picture print out” [the terms might vary]. The difference in price is often 1:10. Use dull—not glossy—paper. It should be mounted flat. As large as possible. Certainly not the best idea to have it 8x10.5.
The camera should be 90ยบ [perpendicular] to the grid. (For some camera trackers the suggestion might be different!) For Zooms, shoot all used settings.
Note that the sensor axis and the lens axis are not always aligned. Ssontech.com has some introductions for that as well.
Back to Cinema 4D. The main idea is to get an representation of the image that comes close to the representation of the rendering [without distortion]. Any movement in the footage is part of the analysis. Distortion from the lens changes locally the speed and with that the precision of the “camera/tracking” solve.
For more information about tracking and lens-grids, check out the book from Tim Dobbert, Matchmoving—The invisible art of camera tracking. Second Edition. [SYBEX] You find the grid discussed on page 173-174, and 280!
Let me know if there is another question.
All the best
