# Intrinsics FocalLength

**URL:** <https://community.nianticspatial.com/t/intrinsics-focallength/1439>\
**Category:** I'm Stuck\
**Created:** [February 10, 2022, 12:43pm UTC](https://community.nianticspatial.com/t/intrinsics-focallength/1439 "2022-02-10T12:43:54Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![tvdz](https://avatars.discourse-cdn.com/v4/letter/t/779978/32.png) [@tvdz](https://community.nianticspatial.com/u/tvdz)\
**Post date:** [February 10, 2022, 12:43pm UTC](https://community.nianticspatial.com/t/intrinsics-focallength/1439/1 "2022-02-10T12:43:54Z")

</div>

Hi guys,

Trying out the ARDK 🙂  
The Focal Length of the depth image and rgb image is very small.  
How do you use this focal length?  
So this focallength is not expressed in pixels ?  
I have to multiply it with the depth.Width and depth.Height?  
I am expecting bigger values so that i can use it as the camera matrix as in OpenCV [OpenCV: Camera Calibration](https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html) .

depth.Width = 144  
depth.Height = 256  
depth.Intrinsics.PrincipalPoint = “(72.0, 128.0)”  
depth.Intrinsics.FocalLength = “(6.7, 5.7)”

For the RGB I get

```auto
    private void _FrameUpdated(FrameUpdatedArgs args)
    {

        var session = _session;
        if (session == null)
            return;

        IARFrame frame = args.Frame;
        if (frame == null)
            return;

        IARCamera camera = args.Frame.Camera;

        _stringBuilderRGB.Clear();
        _stringBuilderRGB.AppendLine($" Resolution: {camera.CPUImageResolution.width} {camera.CPUImageResolution.height} {camera.CPUImageResolution.refreshRate}");
        _stringBuilderRGB.AppendLine($" FocalLength: {camera.CPUIntrinsics.FocalLength.x} {camera.CPUIntrinsics.FocalLength.y}");
        _stringBuilderRGB.AppendLine($" PrincipalPoint: {camera.CPUIntrinsics.PrincipalPoint.x} {camera.CPUIntrinsics.PrincipalPoint.y}");
        Debug.Log(_stringBuilderRGB.ToString());

```

```auto
 Resolution: 1080 2244 0
   FocalLength: 50 50
   PrincipalPoint: 540 1122

```

A focallength of 50 is way too small no?

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<div class="post-metadata">

**Author:** ![Umaiya\_Doddamani1](https://avatars.discourse-cdn.com/v4/letter/u/439d5e/32.png) [@Umaiya\_Doddamani1](https://community.nianticspatial.com/u/Umaiya_Doddamani1)\
**Post date:** [February 11, 2022, 8:04pm UTC](https://community.nianticspatial.com/t/intrinsics-focallength/1439/2 "2022-02-11T20:04:46Z")

</div>

Hello,

The values are surfaced directly from ARKit/ARCore. Focal length is given in units of pixels. The larger the focal length, you will have the smaller field of view for the camera.

50 focal length indicates about 170-degree FOV.

These links explain what the values surfaced directly from ARKit/ARCore  
[https://developer.apple.com/documentation/arkit/arcamera/2875730-intrinsics](https://developer.apple.com/documentation/arkit/arcamera/2875730-intrinsics) and [https://developers.google.com/ar/reference/java/com/google/ar/core/CameraIntrinsics#getFocalLength()](https://developers.google.com/ar/reference/java/com/google/ar/core/CameraIntrinsics#getFocalLength())

Can you share which Unity version and device is being used? Unity documentation includes information about the camera matrix targeted to their version of Unity.

The below link explains the utility of the camera intrinsics.

[https://docs.unity3d.com/ScriptReference/Camera-projectionMatrix.html](https://docs.unity3d.com/ScriptReference/Camera-projectionMatrix.html)

Hope this information helps to resolve your issues.

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<div class="post-metadata">

**Author:** ![tvdz](https://avatars.discourse-cdn.com/v4/letter/t/779978/32.png) [@tvdz](https://community.nianticspatial.com/u/tvdz)\
**Post date:** [February 22, 2022, 4:34pm UTC](https://community.nianticspatial.com/t/intrinsics-focallength/1439/3 "2022-02-22T16:34:19Z")

</div>

It seemed my Unity installation was corrupt.  
I removed all android and unity installations from my device and reinstalled everything.  
And now I am getting valid focallengths.

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<div class="post-metadata">

**Author:** ![Maverick\_Niantic](https://avatars.discourse-cdn.com/v4/letter/m/8edcca/32.png) [@Maverick\_Niantic](https://community.nianticspatial.com/u/Maverick_Niantic)\
**Post date:** [March 5, 2026, 11:50pm UTC](https://community.nianticspatial.com/t/intrinsics-focallength/1439/4 "2026-03-05T23:50:21Z")

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Age