> For the complete documentation index, see [llms.txt](https://stage-precision.gitbook.io/grid/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://stage-precision.gitbook.io/grid/camera-calibration/camera-preparation-and-capture-strategy.md). # Camera Preparation and Capture Strategy Before using the Calibration Object, the physical camera should be prepared correctly. Good camera settings make the Calibration Pattern easier to detect and help produce a more reliable calibration result. This page explains how to prepare the camera and how to collect useful calibration data across the shooting volume. {% hint style="info" %} This page describes general best practices. The exact capture process may differ depending on the selected calibration tool. {% endhint %} *** ## Prepare the Camera Before capturing calibration data, configure the camera to maximize marker detection and image quality. The goal is to keep as many Calibration Pattern markers visible, sharp, and detectable as possible. #### Aperture / Depth of Field Close the aperture as much as practical. Use the highest practical **T-stop** or **F-stop** to increase depth of field. A greater depth of field keeps more Calibration Pattern markers in focus at the same time, especially when Calibration Screens are placed at different distances from the camera. This usually improves marker detection and calibration quality. #### Compensate the Exposure Closing the aperture reduces the amount of light reaching the sensor. Compensate the exposure as needed so the Calibration Pattern remains clearly visible. Depending on the camera and setup, this may include: * increasing ISO or gain * adding more light * carefully adjusting exposure settings Avoid an image that is too dark, too noisy, or overexposed. The Calibration Pattern should remain sharp, visible, and high contrast. #### Focus For a full lens calibration, start with the lens set to **infinity focus**. This gives the calibration a stable starting point and usually allows more distant Calibration Screens to remain detectable. After the initial infinity focus calibration is complete, additional focus positions can be captured if the lens should be calibrated across a focus range. {% hint style="info" %} A greater depth of field generally produces more reliable marker detection and improves the quality of the calibration. {% endhint %} *** ## Repositioning Existing Calibration Screens Some calibration tools can update or reposition Calibration Screens during the calibration process. If this is not your first calibration and the Calibration Screens are already correctly positioned, you may want to disable screen repositioning. This is especially important if the Calibration Screens have already been exported to Unreal Engine, a media server, or another system. If the screens are repositioned during calibration, the external system may need to be updated or re-exported so the complete calibration still lines up. {% hint style="warning" %} Only enable screen repositioning when the Calibration Screen placement should actually be updated. If external systems already use the current screen positions, changing them may require re-exporting or updating those systems. {% endhint %} *** ## Capture Initial Calibration Data Open the Capture Window and begin collecting calibration samples. Start with the camera positioned farther away so the entire stage or calibration area is visible. This gives the solver a broad understanding of the environment before refining the calibration with closer or more detailed views. #### Capture Broad Coverage Move throughout the full shooting volume. Capture samples from different: * positions * heights * distances * rotations * viewing angles Do not collect all samples from one location. A diverse set of camera positions and viewing angles usually produces a better calibration result. #### Include the Outer Boundaries Capture data from the full extent of the area where the camera will be used. This includes the outer boundaries of the shooting volume. The calibration should cover not only the center of the stage, but also the edges and extreme positions where the camera may move during production. #### Collect Enough Data Continue collecting samples until sufficient data has been captured for the current zoom and focus position. The required amount of data depends on the lens, the camera movement, the calibration references, and the selected calibration tool. {% hint style="info" %} Broad coverage is usually more useful than collecting a large amount of data from one camera position. {% endhint %} *** ## Capture Zoom Calibration Data If you are using a prime lens, this section can be skipped. For zoom lenses, calibration data should be captured across the relevant zoom range. #### Start at Maximum Zoom Zoom fully in. Capture calibration data at the maximum zoom position. This helps define the lens behavior at the tightest field of view. #### Evaluate the Zoom Range After capturing data at maximum zoom, enable the solver or camera comparison view used by the calibration workflow. Slowly zoom out while comparing the real camera image with the virtual camera view. Look for zoom positions where the alignment error becomes most visible. #### Capture Additional Zoom Positions When you find a zoom position where the alignment error is high, capture additional calibration data at that zoom level. Move through the space while capturing, instead of collecting all data from one position. Repeat this process as needed until the lens behaves well across the required zoom range. *** ## Capture Additional Focus Data After the initial infinity focus calibration is complete, additional focus positions can be captured if the lens should be calibrated across a focus range. #### Rack Focus Back from Infinity Slowly rack focus back from infinity. Watch the Calibration Pattern detection while doing this. Continue until the system can no longer reliably detect the markers. #### Use the Last Stable Focus Position Return the focus to the last position where marker detection remained stable. Capture an additional set of calibration data at this focus distance. This helps the calibration understand how the lens behaves at a different focus position while still using reliable marker detection. *** ## Refine the Calibration Calibration is usually an iterative process. After the first solve, inspect the result and collect more data where the alignment is weakest. #### Capture Where Error Is Greatest Repeat the zoom and focus evaluation process as needed. Whenever the difference between the real image and the virtual view is greatest, capture additional calibration data at that lens setting and camera position. This helps improve the areas of the calibration that need the most refinement. #### Use Multiple Pattern Configurations When Needed In some cases, one Calibration Pattern size may not be enough. This can happen with tight zoom lenses or setups where the camera sees the Calibration Screens at very different sizes. In these cases, multiple saved pattern configurations may be required. As long as the patterns exist as saved configurations on the Calibration Screens, the calibration tool can automatically recognize them. {% hint style="info" %} For zoom lenses, larger markers can help when the camera is zoomed out or far away. Smaller markers can provide more detailed calibration data when the camera is zoomed in or close to the screen. {% endhint %} *** ## When the Calibration Is Complete The calibration is complete when the real camera image and the virtual camera view remain consistently aligned across the required movement, zoom, and focus range. #### Final Check Check the result by moving through the calibrated shooting volume and changing the lens settings that should be supported. The calibration should remain stable while: * moving through the shooting area * rotating the camera * changing zoom * changing focus * viewing the Calibration Screens from different positions #### Smooth Zoom and Focus For zoom lenses, you should be able to smoothly zoom and focus through the calibrated range while the real and virtual markers remain aligned. If the alignment drifts at specific zoom or focus positions, capture more data at those positions and refine the calibration. *** ## Before Continuing Checklist Before moving on to the Calibration Object workflow, check the following: * The camera image is the raw camera signal. * The aperture is closed as much as practical. * The image is bright enough for reliable marker detection. * The Calibration Pattern is sharp and visible. * The initial calibration starts at infinity focus when performing full lens calibration. * The capture data covers the full shooting volume. * Captures include different positions, heights, rotations, and distances. * Outer boundaries of the shooting area have been captured. * Additional zoom positions have been captured if using a zoom lens. * Additional focus positions have been captured if focus-dependent calibration is required. * Multiple saved pattern configurations are available if one marker size is not enough. * Screen repositioning is disabled if existing Calibration Screen positions should not be changed.