How to set the Camera Internal Parameters - PIX4Dmatic

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Internal camera parameters are a set of characteristics that define how a camera captures images. They include internal geometries of the camera's lens and sensor (focal length, principal point, etc.). These parameters are specific to the camera and remain constant regardless of the captured scene. These parameters are used for the 3D reconstruction; therefore, it is crucial they are accurate to achieve an optimal 3D reconstruction.

How to change the Internal Camera Parameters?

To access the camera's internals:

  1. Click Cameras located at the bottom right of the UI.
  2. Click ButtonInternals.png  on the right side, depending on the specific camera model in question.
  3. The Camera Internals window will pop up.

    PIX4Dmatic_camera_internals_window.png

    Camera internals window.

User Settings

Load optimized parameters Loads the optimized parameters of the camera model after Calibration step is complete.
Reset Reset the camera's internal parameters to the original values taken from the database (or the EXIF tags).
Type of lens

Perspective: Lens that provides a standard, undistorted view of a scene. 

Fisheye: Ultra-wide-angle lens that captures a distorted, panoramic view.

Shutter model

Global shutter or fast readout: Shutter model that captures the entire image simultaneously or with very minimal time difference between pixels.

Linear rolling shutter: Shutter model that captures an image by scanning rows of pixels sequentially, which can lead to distortions with fast-moving objects or during camera movement.

Internal camera parameters

Pixel size Physical size of an individual pixel on the sensor in micrometers.
Sensor width Width of the camera's image sensor in millimeters.
Sensor height Height of the camera's image sensor in millimeters.
Focal length The focal length of the camera in pixels and in millimeters.
Principal point x The x image coordinate of the principal point in pixels and in millimeters. The principal point is located around the center of the image. The coordinate system has its origin as displayed here:

principal point X

Principal point y The y image coordinate of the principal point in pixels and in millimeters. The principal point is located around the center of the image. The coordinate system has its origin as displayed here:

principal_point_X.png

R1 Radial distortion of the lens R1.
R2 Radial distortion of the lens R2.
R3 Radial distortion of the lens R3.
T1 Tangential distortion of the lens T1.
T2 Tangential distortion of the lens T2.

Camera included in the database

PIX4Dmatic has an internal camera database with the optimal parameters for a plethora of camera models. If the images are from a camera model included in the database, the Internals window will be automatically filled with the optimal parameters set by the database.

Camera not included in the database

When the camera model is not included in the database and the EXIF tags do not provide enough information to create a generic camera model, a warning icon will appear in the Status Center. A message will be displayed: 


    Image EXIF tags are not sufficient for creating a generic camera model.
Camera internals need to be edited before processing.

The Button.png window will be incomplete:


PIX4Dmatic_internals_edit.png

Camera internals window.

The required information must be filled out before Processing. This information can usually be found in the official documentation provided by the camera manufacturer. Manufacturers typically provide datasheets that contain technical specifications, including sensor and pixel size, focal length, and other relevant details.

 
Note: For camera models that are not supported and the official documentation does not provide sufficient information about the principal points x and y, it is recommended to assume that the principal point for x and y is in the middle of the image sensor. The Calibration step will then optimize these values.

Edit user database

PIX4Dmatic enables the option to add or remove a specific camera model to a personal user database that can be used for future projects, by selecting the respective box at the bottom of the Internals window and clicking OK.

   New or unknown camera models

For new or unknown camera models, the following step-by-step guide is recommended:

  • Add (approximate) values in the Camera internals window.
  • Run Calibration step.
  • Open the Camera internals window and click on the Load optimized parameters button.
  • Run Reoptimization.
  • Open the Camera internals window and click on the Load optimized parameters button.
  • Run Reoptimization.
  • ...
  • Repeat until the values (before and after the Load optimized parameters button) converge.
  • Save to the user database by ticking the respective box and then click OK.

 

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