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The M1 stores a camera calibration (Double Sphere intrinsics) and an IMU field calibration (bias, scale-misalignment, noise and temporal terms, and the camera-to-IMU transform). Both are provided with the device and persist across reboots, and both are published as recording metadata so that a downstream consumer can determine the values a session was captured under. All calibration writes require an IDLE device and take effect on the next capture session.

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Read the current calibration

From the library, the calibration is available in the cached device snapshot:

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Camera intrinsics

Intrinsics are produced by a checkerboard solve. The calibrate_camera tutorial displays the live feed with a detection overlay, captures 40 views as the board is moved through the frame, fits the model, and offers to write the result to the device. Move the board across the full frame and vary its tilt between captures; a set of near-identical frontal views produces a poor fit.
To write a set of intrinsics obtained elsewhere:
--set replaces the stored intrinsics entirely, and the camera factory default is all zeros, meaning uncalibrated. ef-cli calibration --camera --reset restores that default rather than the calibration the device was shipped with. Record the current values before overwriting or resetting them. Each recording carries the intrinsics it was captured under, so an existing MCAP also serves as a record of them.

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On-device rectification

By default the M1 delivers raw fisheye frames under the double-sphere model and publishes the intrinsics alongside them, leaving rectification to the host. Enabling rectify causes the device to undistort the frames it produces, so recordings contain rectilinear images instead. The change takes effect from the next capture session.
The flag-only form reads the stored calibration, modifies only the named flags, and resends it, so the intrinsics do not need to be re-entered to change rectification. fov_scale must be positive and applies only when rectify is enabled. The intrinsics remain in the recording metadata in either configuration, so a host consumer can perform rectification instead. ef-cli config reports the current rectify and fov-scale settings alongside the capture mode.

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IMU calibration

The calibrate_imu tutorial measures gyroscope zero-bias with the device held still, then fits the accelerometer ellipsoid as the device is rotated through all orientations. It writes the result to the device, replacing the stored calibration.
A run with insufficient orientation coverage, or one in which the device was not held still, is rejected with guidance rather than persisted. Repeat the procedure rather than retaining a poor calibration. Select how recordings carry the result:
Every recording carries the parameters as metadata regardless of the selected mode. In calibrated mode the embedded parameters are marked as already applied, which prevents a downstream consumer from applying them a second time.

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Reset

Both restore the factory default for the selected sensor. For the camera that default is all zeros, so read the warning above before running it.