Features
HDR+
Basic: HDR+ is Google's proprietary image processing routine, and is more than just traditional "HDR' modes. HDR+ employs image stacking to control exposure, and also to preserve details, reduce noise, increase sharpness, etc. It is an all-in-one package.
Zero Shutter Lag (ZSL) HDR+
The Pixel 1 introduced ZSL HDR+ which means when you open the camera, the system utilizes the Hexagon DSP to constantly buffer frames and marks the time slot of when you pressed the shutter button.
Quote from Marc Levoy via The Verge:
"The moment you press the shutter it's not actually taking a shot — it already took the shot," says Levoy. "It took lots of shots! What happens when you press the shutter button is it just marks the time when you pressed it, uses the images it's already captured, and combines them together."
It's a major usability improvement on the HDR+ mode in last year's Nexus 6P and 5X. "What used to happen last year is you'd press the shutter button and you'd get this little circle going around while it captured the images you need for the burst; now it's already captured those," says Levoy. "And that's big, because that means that you can capture the moment you want."
Simulates bokeh for improved subject separation from the background. The front camera of the Pixel 2 only provides Portrait Mode when a human face is detected, and the rear camera can work on an object, an animal, a human, etc because it uses information from the Dual Pixel PDAF sensor to detect depth. Google Camera ports for non-Pixel phones can NOT do this so all ports for non-Pixel phones utilize the front camera technique for both front & rear (which means all ports for non-Pixel phones can only properly apply bokeh when a human face is detected).
Motion Photos
Provides short clips of moments before and after you take the photo.
Top Shot
When Motion is set to Auto or On, Pixel will recommend a better photo to you if it detects one. Like if you captured a photo when someone blinked.
Photobooth
Automatically capture a photo when Pixel detects a silly face or a smile.
Super Res Zoom
Enhances zoomed picture quality by purposely shifting the camera module using OIS (Pixel 3 only) to gather more data.
