Back to How to Set Up Tracking Systems in Aximmetry
Introduction
This document discusses the importance and challenges of camera calibrations from the perspective of virtual production.
The Concept of Camera Calibration
The Concept of Camera Calibration consists of two parts: lens calibration and tracking calibration.
The Concept of Lens Calibration
The concept of Lens Calibration is that the studio camera lens's intrinsic characteristics (such as lens distortion, center shift, etc.) always distort the image and its colors while the virtual camera (the studio camera's virtual counterpart) by default gives us a perfect image (no distortion of image and/or colors). The lens calibration's goal is to calculate the studio camera lens's intrinsic characteristics (including its field of view). For precise blending of the camera input and the virtual world, we need to adjust the virtual camera's characteristics to the calculated values.
The Concept of Tracking Calibration
The concept of Tracking Calibration is that the tracking system can only measure the position and rotation of its tracking device, whereas the virtual production requires the position and rotation of the studio camera's no-parallax point (close to the camera sensor). The tracking calibration's goal is to calculate the difference between these two locations and rotation.
NOTE: To learn more about Studio Cameras and Virtual Cameras, you may refer to the following articles:
link to SC
link to VC
What Do You Need to Calibrate a Camera?
Many tracking systems and lens encoders provide all the necessary tools you need to calibrate them.
Aximmetry also provides tools to calibrate any supported tracking system and lens encoder with ease. Its flexibility even allows it to be used together with 3rd party calibration solutions.
NOTE: You can always use Aximmetry to calibrate your tracking/lens encoder system, and in many cases, you have the additional option to choose between the tracking/lens encoder system's native calibration solution and Aximmetry's tools.
Steps of a Camera Calibration
Depending on the type of tracking (or lack of it) we choose for the studio camera, the calibration process consists of one or both of the following steps:
Lens Calibration
During lens calibration, we measure the lens characteristics, such as the field of view of the studio camera or the lens distortion of the camera lens, among others.
This can be used even in cases where the studio is not equipped with any tracking device.
NOTE: PTZ cameras have built-in lens encoders/lens servos.
NOTE: For single focal lengths and zoom lenses, you can choose to calibrate one focal length without any additional hardware.
NOTE: To calibrate the entire focal range of a zoom lens, you will require the use of a lens encoder.
NOTE: 1 lens encoder can only encode 1 lens ring. Most modern camera lenses have 2-3 rings: a zoom ring, a focus ring, and (in some cases) an aperture ring. You will need as many lens encoders as many rings you want to encode.
Tracking Calibration
During tracking calibration, we measure the distance and rotational difference between the tracking system's point of measure (the tracking device) and our studio camera's no-parallax point (close to the camera sensor), since our ultimate goal is to learn the studio camera's point of view.
NOTE: Using Aximmetry's Camera Calibrator, PTZ cameras do not require additional tracking calibration, but they do require lens calibration.
Starting of a Camera Calibration
To begin calibrating your camera with Aximmetry, you have two options:
Use Aximmetry Basic Calibrator for manual calibration of your camera or the adjustment of existing calibration profiles.
Use Aximmetry Camera Calibrator for the automatic calibration of your cameras.
