Lens Calibration Tool unable to calibrate for multiple focal length values

[dThomas]

Hello,

I am currently working on a virtual production setup where I want to combine a VCam with live video from a physical camera.

At the moment I am having problems performing the lens calibration using the plugin.

I am using a CinemaCameraActor with an added Lens component linked to my Lens File and using evaluation mode Use Camera Settings:

When I open the Lens File I can select the live video Media Source, enter basic information like sensor size and name. I adjust the focus settings (like focal length and focus distance) of the CameraComponent to match settings of the physical camera and then start the first calibration step: Lens Distortion.

So far everything is fine, I can capture the checkerboard and add calibration images to cover the complete field of view for the current focal length. When all frames have been captured I hit Add To Lens Distortion Calibration. But now I want to repeat the process for another focal length as it is recommended by the official documentation of the calibration plugin, but after hitting Add To Lens Distortion Calibration the focal length of the CameraComponent jumps to some computed value and can not be changed any longer. So I am not able to do the calibration for other focal length values. When looking at the Lens File Panel I can see calibration data for my first focal length has been calculated but I am not able to add calibration for other focal length values.

I tried to capture calibration images for multiple focal length values before hitting Add To Lens Distortion Calibration but the result in the Lens File Panel is just calibration data for the focal length value of the last captured frame.

So I would be glad to get some advice what I am doing wrong and how to calibrate lens distortion for multiple focal length values?

[dThomas]

I managed to find the solution for the problem.
The lens calibration tool seems to work only with Live Link FIZ data present, despite there are other options that you can select neither of them seem to work. The following tutorial shows how to create a virtual Live Link subject to manually control focus, iris and zoom values if you don’t have an actual Live Link source from your physical camera: Camera Lens Calibration for Production | Unreal Engine 4.27 Documentation

With the virtual subject in place I can adjust the current focus, iris and zoom values used by lens calibration through the virtual Live Link subject.