The iPhone 8 features a unique portrait mode that allows users to apply unique lighting effect to the face of the photographed person. It uses facial detection and depth maps to capture unique and more creative portrait pictures. The iPhone 8 Portrait Lighting mode mimic studio effects. It analyzes the image using machine learning algorithms in real-time. The phone can then differentiate between the face and body of the person and its surrounding. One that data is obtained, users will have the option to change the lighting straight away or after they have taken the image using the Photos app. This also means that this works in a non-destructive manner so you can still keep your original shot image.
Users can also produce a depth of field effect that simulates bokeh effect. Using this effect, the background behind the subject is blurred out in a degree chosen by the user. This creates a more defined contour around the subject by blurring out distracting background elements.
Those professional-grade effects won't be possible outside of a studio setting and Apple now made it possible digitally using this unique Portrait mode. For example, if you ever wanted to create a Stage light where the subject face spotlit against a deep black background, you would need a three light setup with a Key Light, Fill Light, Background Light and some accessories to achieve that. I've also seen that achieved with one strobe and an off-camera flash shot into an umbrella.
Here is a video by Glyn Dewis that demonstrate how to achieve this effect outdoors using a DSLR camera and simple strobe setup.
This unique iPhone 8 Portrait Lighting mode offers several tweaks that allows you to change the results to your liking. For example, you can apply Natural Light , Studio Light, Contour Light, Stage Light and Stage Light Mono. Each mode gives you a new fresh and creative look. This is a huge and important camera features that take use of the advanced hardware of the iPhone 8. Just think about it, how amazing it will be being able to capture professional studio-grade portraits without any expensive setup, just using your iPhone 8. Keep in mind that this isn't a photo filter of some sort but adjustments to the actual image information. This is also a much more advanced feature compared to the iPhone 7 Plus "Portrait Mode".
Overall, one of the more interesting camera features that you won't get anywhere else other than the iPhone 8, iPhone 8 Plus and iPhone X. I'm sure there are filters out there that can mimic this effect, but they will definitely won't be at the same grade than what you get with the iPhone 8 due to the required hardware for achieving these professional results.