Refine Calibration
The refine stage is where the majority of the "work" of a lens calibration is conducted.
On this page a user is able to modify every parameter of the existing calibration points while also being able to create completely new points to either improve interpolation between existing points or fill holes where points are missing.
At the end of this stage the lens graph should be complete and checked and the lens ready to use.
Start by moving to one of the calibration points, the fully wide, infinity point is typically the best one to begin with
Select the point in the graph view to display it's parameters
Pan the camera so that the centre of the calibration grid is positioned on the side of the frame
Observe closely for any drift in the position of the calibration grid, if drift is detected make adjustments to the parameters to bring it into line
When happy with the calibration point, choose "Confirm Point" to save the changes and repeat the process for the other calibration points
If calibrating a Non-Zoom lens, it's unlikely that any "holes" are present in the lens graph. However, when working with a zoom calibration it's expected that there is a large part of the lens graph that is currently incomplete. This is shown in red in the image below
It's very important that lens information is populated for this area, otherwise, when the focus/zoom travels to this region then the interpolation is likely incorrect
To fill the holes in, it is possible to manually add calibration points in the Refine stage. This can be done by either using the chart or by manually entering the values
Move to a part of the lens that is not calibrated currently, It is recommended to try and match the structure of the lens graph and keep the calibration points in ordered rows and columns
Press "Add calibration point at the current position" to create a calibration point at the current position of the lens encoders
Press "April Tag Calibration" to calculate lens calibration information at this point, follow the same steps that are described in the earlier "primary calibration points" step
Alternatively. Manually adjust the calibration point without using the chart and purely using the calibration grid as a reference
Manually creating and adjusting points without the chart is a quick and efficient way to quickly complete a lens file, particularly when zoomed in as distortion is typically less present in these parts of the lens
Repeat this procedure until the lens graph is complete
Depending on the lens you are calibrating it may be necessary to add more calibration points on either the zoom or focus.
Use the calibration grid graphic to help identify areas where more data is required and add calibration points as needed