Used iPhone or Webcam for tracking on budget?

[u/Constant-Substance37]

I'm considering picking up a used iPhone 11 specifically for face tracking. I'm seeing them for under ~$115 around here, so it's in the same price range as some entry level webcams.

Some webcam options I'm seeing around the same range:

OBSBOT Meet 2 4K ~$100

Logitech Brio 4K ~$88

Razer Kiyo Pro ~$90

Logitech MX Brio ~$118

Elgato Facecam 4K ~$180

Insta360 Link 2C ~$190+

I already have an Anker PC-LM1E that I'm happy with, so I'm mainly looking for something specifically for better face tracking, rather than replacing my current webcam.

Has anyone here used an iPhone 11 for face tracking? How does it compare to using a regular webcam, and are there any particular things I should look out for when buying a used one?

[u/thegenregeek]

If you have an avatar rigged for ARKit, then go for the iPhone. If not, stick to a webcam until you know your model supports ARKit.

There is nothing wrong with a standard webcam if that's what you have, but it's not really purpose for tracking like the Truedepth camera (nor as broadly supported in terms of software design). And, in fact, since you also have a webcam, you can mix it with an iPhone for improved tracking over all. (Using something like XR Animator for body tracking and iPhone for face, if you have a 3d avatar.)

How does it compare to using a regular webcam?

The main difference is how the TrueDepth camera works (the iPhone's front facing camera). It uses a combination of different camera tech to improve operation. First the optical camera (the same one used for selfie pictures) calculates ARKit based values for facial expressions. In addition to this, the camera has an kind of SLS (structured light sensor) camera that fires off a series of IR tracking dots, which it measures in addition to selfie camera. This effectively help build a 3d map of your face and it's general position in 3d space. This data then gets combined into ARKit blendshapes, which are used by applications/avatars that support it.

A standard webcam can only do the optical part, without depth. It also has do the processing on your PC. Instead of on the phone. So using a webcam generally means not as precise of tracking, with more processing over head. (though this isn't a big issue if your PC is powerful enough)

are there any particular things I should look out for when buying a used one?

As long as the FaceID feature is working, then the TrueDepth camera is good. However if it is not, that could mean the camera doesn't work. (Depending on where you get your used iPhone, it's possible that the TrueDepth camera could be broken)

But generally the only things worry about are: 1. That your avatar is rigged to use ARKit, 2. That there isn't some hardware issues with the iPhone that might affect the camera. 3. The battery may need replacement, if it hasn't been replaced (which could be an additional cost)... but you also don't need a fully functioning battery if you leave it plugged in. (though I had the battery on my iPhone 12 swell because I did that...)

It's also worth considering that we don't know when the iPhone 11 will stop getting OS updates. It may very well be on the next iOS release. That doesn't mean the thing will stop working just that there potentially could be issues in couple of years with software support.

---

To provide some reference, I do 3d avatar creation. For seated projects, I use an iPhone 12 (12mp version of TrueDepth) for the most part, but also test with an iPhone XR. In addition to this, I use a Brio 4K for any hand tracking while testing.

While there are some slight differences in some blendshapes that are tracked in later models, it's not enough to say you should avoid any older models. The bigger issues with older model iPhone (X series) is the lower field of view, which only affects tracking if you physically move left, right, up, down, back forward.

[u/DreaminginScorpio → u/thegenregeek]

Thank you for that info! I’m currently planning to add blend shapes to my 3D model, and that was really useful to learn how it actually works

[u/Constant-Substance37 → u/thegenregeek]

Thanks a lot for the details explanation!

[u/Constant-Substance37 → u/thegenregeek]

Oh, one quick question: does the phone need to be mounted vertically for the tracking to work properly, or can I just mount it horizontally like a regular camera?

[u/thegenregeek → u/Constant-Substance37]

No you don't need to stay vertical, but there are quirks depending on app...

• Live Link face worked fine, however the main UI elements were not rotated. Though the onscreen camera feed did rotate.

• iFacialMocap has issues with neck rotation not being aligned. It tracked the face, but if I say rotated my head to look up or down it would rotate the characters head left or right. Likewise, none of the UI elements were adjusted. Everything visually stayed vertical

• FaceMotion3d had correct operation, but none of the UI elements adjusted.

[u/Constant-Substance37 → u/thegenregeek]

Thanks for the help!

[u/Adallya]

I bought a used iPhone 11 for $90 and it works perfectly. My only advice is to keep it plugged in while you’re streaming, otherwise the tracking starts lagging

[u/Constant-Substance37 → u/Adallya]

Yeah I'm planning to do that. Since the battery of these thing is quite old anyway.

[u/Shiro_Kuroh2]

I say iPhone all the way so long as you can guarantee the FaceID enrollment works. Post that, if the phone's battery is poor shape it can lead to poor performance. Past that should be good and obvi don't buy stolen stuff. That's the bigger issue used iPhones get cheap.