Question: Can anybody explain, what is the 100% Focus Pixels feature available in the iPhone 11 Pro?
I would also like to know what could it mean for developers working on photo and video editing apps, I mean how can we use it for our app's capturing quality result.

Answer: 
A "focus pixel" is a term Apple coined for camera pixels with a mask placed over half of it to limit the light angles that can reach that pixel ([source](https://techcrunch.com/2018/09/25/see-the-new-iphones-focus-pixels-up-close/)). Comparing pixels with masks on one side against pixels with masks on the opposite side allow for the camera phone to perform passive autofocus via onboard computation ([wiki](https://en.wikipedia.org/wiki/Autofocus#Passive)). Traditionally the number of focus pixels were limited as masking half of the incoming light angles results in noisier signals from those pixels. 

However it is likely that developments in noise reduction algorithms (via [neural networks](https://www.cnet.com/news/iphone-11-pros-new-deep-fusion-is-coming-to-boost-your-photos-take-on-google/) and otherwise), [HDR](https://en.wikipedia.org/wiki/High-dynamic-range_imaging), and potentially the sensor itself has resulted in the tradeoff being in favor of more focus pixels which allows for faster, higher resolution autofocus calculations, particularly in low light.
I have not exactly knowledge of that, But I have read some cutting edge of topics on that on below websites which have some following explanation. I hope this will help you.

**Source:** <https://www.news18.com/news/tech/apple-iphone-11-series-finds-a-lot-of-its-intelligence-from-ios-13-2304277.html>

> 
> There will be advanced software working to understand the data from
>  the 100% Focus Pixels on the new wide sensor. Next generation Amart
>  HDR, better dynamic range calculations and analysing the data from
>  each pixel to improve the noise reduction are highlights that will
>  make a presence felt on almost every photo that you click.
> 
> 
> 

**Source:-** <http://betterfamilyphotos.blogspot.com/2014/09/what-are-apple-iphone-6-focus-pixels.html>

> 
> Apple has not yet been clear on what exactly they mean by "Focus
>  Pixels." However, in their keynote, they mentioned that it's a
>  technology that's found in DSLRs, and they also showed a demonstration
>  of the iPhone's continuous autofocus. Both of those point to Focus
>  Pixels being either phase detection or a hybrid autofocus that uses
>  both phase detection and contrast detection.
> 
> 
> 

To deeply know about Focus Pixels: <https://techcrunch.com/2018/09/25/see-the-new-iphones-focus-pixels-up-close/>