The Movie Camera Presets panel is composed of four main areas:
The Calibration Manager (1), where media can be loaded ready for calibration
The Active Metadata Window (2), where metadata present in the media is displayed, and can be connected to the virtual camera for use during calibration.
The Camera Preset parameters (3), where camera body and lens parameters can be adjusted if required, and where the camera preset is built
The Focal Range graph (4), where calibration patterns for individual focal lengths are displayed.
The Calibration Manager displays information about the current clip that is loaded for calibration:
The following buttons are also available:
- Clicking this button will display the File Browser where media can be loaded.
- Clicking this button will display a calibration pattern which can be shot directly on the desktop.
- Clicking this button will remove any media loaded and reset the panel to its default state.
PFTrack supports both checkerboard and a regular grid of calibration dots (black dots against a white background). Either pattern can be used for calibration, although if a choice is possible we recommend the new calibration dots pattern as it is often able to provide more accurate detection and calibration results.
The dots pattern can be displayed full screen directly from withing the PFTrack UI (for example, to project onto a screen for image capture). To do this, click the button.
This will display a popup window showing the keyboard controls:
+ increase the pattern size,
- decrease the pattern size,
Esc Close the window.
Clicking the OK button will display the calibration pattern full-screen. To ensure a large enough number of calibration points are detected, the grids should be shot front-on, filling as much of the image area as possible:
When calibrating zoom lenses, it is recommended to shoot calibration patterns at different focal lengths over the entire focal range of the lens. For example, a 50-150mm lens could be sampled with one calibration pattern every 10mm. For focal lengths between these samples, the lens distortion model will be interpolated. Lenses with a significant change in distortion over their focal range may require more calibration patterns to be shot.
For prime lenses, a single calibration pattern will suffice.
When loading media from the File Browser, an additional option is available where the type of calibration pattern can be selected:
The pattern type can be changed between:
- A regular grid of calibration dots
- A uniform checkerboard pattern.
Once media is loaded, the Movie Playback controls can be used to play through the clip, or the Left and Right keys used to move one frame backwards/forwards.
Alternatively, the Frame Scrub Overlay (2) can also be displayed by either:
- Clicking the button (1) to the left of the playback controls
- Pressing and releasing the Alt key (press and release again to remove the overlay)
- Pressing and holding the Alt key (release the key to remove the overlay)
When the overlay is visible in the Cinema window, clicking and dragging with the left mouse button will change frame. A yellow indicator is show at the current frame, along with the current frame number
After loading a clip, the Active Metadata window will display any metadata available to use in the top-left of the PFTrack window:
Information related to the Camera Body is shown at the top (1), and Camera Lens in the middle (2).
The full list of all metadata in the media is shown in the RAW Metadata section (3). The important values that PFTrack has identified are highlighted in blue. Individual sections of the RAW Metadata list can be opened and closed using the white arrow buttons to the right of each section title.
If metadata is available to use, it must be connected to PFTrack's virtual camera in order to populate the camera preset data. This is achieved by clicking the Connect toggles next to each piece of metadata:
: When in this state, metadata is not connected and is not being used (this is the default state).
: This state indicates the metadata value is to be used as a Hint (for example, to find the best matching camera model containing sensor size information).
: This state indicated the metadata value is to be used exactly as presented.
Not all states are available for each parameter input.
Each camera preset contains information describing both the camera body and lens. These are separated out into two section of the panel:
A set of sensor size presets are available in PFTrack for both RED and ARRI cameras. These can be activated by selecting a suitable Camera Make and Camera Model from the available options:
Where appropriate, a Shooting mode can also be chosen. Please note: it is important that these values are set correctly as they will influence the size of the sensor area used to capture the image, especially when using windowed sensors. For example, when shooting with a full frame 5K image sensor but working with a 2K proxy clip, it is important that the shooting mode is set correctly to the 5K mode, rather than the 2K image size, as this will have a significant effect on the sensor area. For a windowed sensor (as shown above) the sensor size is 25.6 x 13.5 mm full frame, or 10.2 x 5.4 mm when shooting in 2K mode.
If no sensor information is available, it can be entered manually by selecting Unknown from the Camera Make and Camera Model options and entering the data manually:
In this case, the Sensor resolution (measured in pixels) and Sensor area (measured in millimeters) should be entered. Note that these values should correspond to the full sensor size of the camera.
Once the sensor area is entered, the following two buttons can be used to select between a windowed and scaled sensor mode:
: This specifies a windowed sensor, where the actual sensor area used to capture the image is a smaller section in the centre of the sensor.
: This specifies a scaled sensor, where the data captured by the sensor is scaled to fit horizontally or vertically.
The choice of a windowed vs. scaled sensor directly affects the Image area (measured in pixels) which corresponds to the sensor area used to capture the image.
The Camera Lens panel contains the lens make, model, serial number and squeeze factor if relevant:
The Lens Type can also be selected using the following buttons:
: When this button is active, the preset will be for a Prime lens, calibrating lens distortion a single focal length.
: When this button is active, preset will be for a Zoom lens, where lens distortion can be calibrated at multiple focal lengths.
: When this button is active, a spherical lens distortion model will be used.
: When this button is active, an anamorphic lens distortion model will be used.
When using a zoom lens, the focal range over which lens distortion can be calibrated is specified using the Fl min and Fl max values.
The Calibration panel is where lens distortion can be calibrated, and a camera preset generated:
In order to calibrate lens distortion, the following conditions must be satisfied:
- The Sensor area in the Camera Body parameters has been set.
- The Focal length value has been set for a prime lens, or the Focal range has been set for a zoom lens
- One or more calibration patterns have been detected in the source media.
If you have loaded a movie clip rather than a single frame, use the button in the Cinema window to display the Frame Scrub Overlay, and then move to the frame containing your calibration pattern using the left mouse button.
Automatic calibration grid detection
To detect the calibration pattern, click the button.
PFTrack will attempt to read a focal length value for the frame from media metadata. If no such value can be read, it will display a popup window where a focal length can be entered:
The calibration pattern will be detected automatically, with one point at each checkerboard corner or calibration dot, depending on the grid type specified when loading the media.
As each calibration pattern is detected, it will be displayed in the Focal Range Graph at the top of the presets panel:
Individual calibration patterns can be selected for display in the Cinema window by clicking on the focal length at which the calibration pattern was generated.
For prime lenses, detecting a single calibration pattern is enough to calibrate lens distortion.
For zoom lenses, calibration patterns should be detected at different focal lengths over the entire focal range. The exact number required will depend on how much lens distortion changes over the focal range.
Editing the calibration grid points
Once the calibration grid points have been detected, tools are available to adjust or delete any incorrectly located points and also set the region of interest for the calibration grid. These tools may be useful when using bi-level grids whose points cannot all be detected automatically.
- This button allows the detected calibration grid points to be moved, or new grid points to be created using the left mouse button in the Cinema window. When placing new grid points, the mouse location will snap to the nearest detected corner unless the Control key is held.
- This button allows detected grid points to be deleted by clicking and dragging with the left mouse button to draw a selection rectangle. All points inside the rectangle will be removed once the left mouse button is released.
The Undo and Redo buttons are available to correct any mistakes, and you can also click the button to start the detection process again and restart if required.
Solving for lens distortion
Once calibration patters have been detected at one or more focal lengths, the button can be clicked to start the calibration process. As calibration proceeds, information will be written to the log file indicating the accuracy of the distortion information represented as mean error, standard deviation, and maximum error:
A006_C003_0302QB frame 1: 'Spherical' focal length= 50 mm; Mean error 0.52 pix; std 0.27 pix; max 1.71 pix A006_C003_0302QB frame 6: 'Spherical' focal length= 100 mm; Mean error 0.54 pix; std 0.29 pix; max 1.62 pix A006_C003_0302QB frame 11: 'Spherical' focal length= 149 mm; Mean error 0.95 pix; std 0.49 pix; max 2.30 pix
The calibration pattern points displayed in the Cinema window will also be coloured to indicate the accuracy of the calibration, from red to orange and green, and will undistort the source media using the calibrated lens distortion model.
Once calibrated, clicking and dragging with the left mouse button in the Focal Range Graph will display the field of view of the camera at the current focal length:
A wireframe undistorted representation of the source media will also be displayed in the Cinema window. This can be used to check how lens distortion will be interpolated between focal lengths at which it has been calibrated:
The buttons at the bottom of the Calibration panel can be used to switch various display components on or off:
- This button will toggle display of the sensor overlay information.
- This button will toggle display of the undistorted wireframe.
- This button will toggle display of the calibration points.
Adjusting image size
After lens distortion has been calibrated, controls are available to adjust the image size if required
By default, a clip will undistort to display the maximum available image size (up to a limit of 16K). If desired, this can be changed to undistort the image whilst keeping the original image size fixed. Choosing this option will mean some pixels will be lost around the boundary of the image.
: Clicking this button will change the image size to display the complete undistorted image (up to a limit of 16K).
: Clicking this button will change the image size to match the original source material resolution.
Distortion Centre: This displays the estimated centre of lens distortion in the original source image.
Field of view: This displays the current horizontal and vertical field of view after undistorting the image.
Finally, once lens distortion has been calibrated, the preset can be stored in the Preset Manager panel by clicking the button. This will display a popup window asking for a preset name. Clicking the Accept button will store the preset in the project.
Once presets have been stored, they become available for use in the Clip Input nodes.
The Preset Manager panel lists all movie camera presets that are currently available in the project:
When PFTrack launches, any preset files stored in the user's documents folder
/Users/USERNAME/Documents/The Pixel Farm/PFTrack/presets/camera (or an alternative location as specified in the Preferences window) will be automatically loaded into the project.
Individual presets can be selected for export by clicking with the left mouse button, and managed using the following buttons:
: Clicking this button will export the preset as an XML file. When saving a preset, ST-maps can also be saved in OpenEXR format alongside the XML file if required. This is controlled by the related option in the Export Preferences.
: Clicking this button will import a preset XML file.
: Clicking this button will remove the preset from the project.