If you look at photographs of the new Fairphone 4, it looks as if there were 3 camera lenses, (e.g.:
Making the fair choice easier: Fairphone 4 is here - Fairphone
But if you read the spec, there are only two ("+ 1 selfie-lens" on the other side)
==> what is the third “circle”? dummy for future camera updates? fingerprint sensor (would be the worst place to put a fingerprint sensor - you’re going to tap to the camera lenses all the time!
There’s a couple of reviews saying it’s an empty slot., but reading the description of the camera module, I think it’s a light and colour sensor - not sure though.
It is a 1/2 inch light sensor for the main camera.
The Fairphone 4 rear cameras are the real deal. A replaceable pair of premium lenses for all the details (48MP main) or the bigger picture (48MP ultrawide). Add a light and color sensor for blazing fast autofocus and top it off with OIS for a shake-free shooting experience
Fairphone 4 Rear Cameras - Spare Part | Fairphone
Hi there,
So I’m considering getting a fp4 soon. But like everything I buy I tend to spend too much time searching for answers to a ton of questions before actually purchasing the product.
It appears there’s an empty “camera slot” in the back of the phone, any idea what it’s meant for ? Couldn’t find any reference to it in the FAQ
Welcome to the Fairphone community.
What exactly do you mean with ‘empty camera slot’?
If you refer to the third circle on the backside near the two cameras, it’s a sensor.
It’s a light and colour sensor 
Primary Camera - OIS Camera
48 megapixels resolution with 48 megapixel output
0.8um, 8000x6000 (48MP)
Dual LED flash, detected single tone
1/2" sensor
The 1/2" sensor is the size of the main camera sensor, not the ’ light and colour sensor’.
Isn’t that the same thing? Asking because I’m still not entirely clear on what’s behind that circle.
I can’t find within the promo videaos released by Faiphone, which I did see so here is >
Fairphone gives the device a laser autofocus and time-of-flight sensors as well as a color sensor,
https://www.reddit.com/r/Android/comments/px813y/fairphone_4_5g_in_detail_fair_smartphone_without/
Ah! Found this
The replaceable Rear cameras part hosts:
- a primary lens for all the details: Wide (W) - 48MP output.
- A separate lens for the bigger picture: Ultra-Wide (UW) - 48MP output.
- A light and color sensor for fast autofocus.
https://support.fairphone.com/hc/en-us/articles/4410238693649-FP4-Cameras-
It’s not the same thing. One circle is the 1/2" main camera sensor, one is the wide angle camera sensor, ant the third is either the ‘light and color sensor for fast autofocus’ or the ‘Time-of-flight (ToF) laser autofocus assist for fast focusing’.
I think the third contains all of those.