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# focalLength

The camera’s focal length, in millimeters.

```
var focalLength: CGFloat { get set }
```

## Discussion

The [`sensorHeight`](/documentation/SceneKit/SCNCamera/sensorHeight) and [`focalLength`](/documentation/SceneKit/SCNCamera/focalLength) properties determine the camera’s horizontal and vertical viewing angles using terms that model physical camera devices. (Alternatively, you can work with viewing angle directly though the [`fieldOfView`](/documentation/SceneKit/SCNCamera/fieldOfView) property.) For example, with the default sensor height of 24 mm and default focal length of 50 mm, the vertical field of view is 60°.

Setting the [`fieldOfView`](/documentation/SceneKit/SCNCamera/fieldOfView) property causes SceneKit to automatically recalculate the [`focalLength`](/documentation/SceneKit/SCNCamera/focalLength) value, and setting the [`sensorHeight`](/documentation/SceneKit/SCNCamera/sensorHeight) or [`focalLength`](/documentation/SceneKit/SCNCamera/focalLength) property recalculates [`fieldOfView`](/documentation/SceneKit/SCNCamera/fieldOfView).

---

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