Great question—this is a common point of confusion when working with iOS camera hardware parameters. Let's break down your two questions clearly:

1. Why the FOV discrepancy between the reference table and activeFormat.videoFieldOfView? #

The core reason comes down to what each value represents:

• The reference table you're using lists native hardware FOV values, which correspond to the physical lens paired with the full sensor area (typically for photo mode or the highest-resolution, uncropped video format). These are precise, lab-measured hardware specs.
• The activeFormat.videoFieldOfView returns the effective FOV for your selected video format, which can vary based on how the sensor is being utilized:
  • Pixel Binning: In your iPhone X example, the 720p format is marked as binned. Binning combines multiple sensor pixels into a single output pixel, allowing the camera to use a larger portion of the sensor's area—resulting in a wider FOV than the native full-res spec. That's why the API returns 69.654 instead of the reference table's 60.983.
  • Cropping: Conversely, some high-resolution video formats (like 4K on certain models) crop the center of the sensor, which would result in a narrower FOV than the native value.
  • Software Adjustments: The API's value might also include minor software corrections for lens distortion, whereas the reference table could be the raw physical FOV before correction.

Since you're targeting precise hardware specs, the reference table's native values are indeed more reliable for consistent cross-format calculations.

2. How to get FOV reference data for newer iPhone models (Xs, XR, 11 series, etc.)? #

Apple hasn't published an official updated version of the Capture Format Specifications table for post-X models, but you have a few practical options:

• Manual Measurement: Use a controlled setup (a known-size target at a fixed distance) and calculate FOV using the formula: FOV = 2 * arctan((target width / 2) / distance). This gives you precise, device-specific values tailored to your use case.
• Traverse All Capture Formats: Write a small test app that iterates through all AVCaptureDeviceFormat instances for each camera (wide, ultra-wide, telephoto) on the target device, then log the videoFieldOfView for each format. You can compile these values into your own internal reference table.
• Community-Collected Data: Many iOS developers share their measured camera specs on technical forums or open-source repositories. Look for discussions or curated lists where other developers have documented FOV values for newer models (just make sure to verify the data with your own tests if precision is critical).

内容的提问来源于stack exchange，提问作者LinChiSin