Google Camera has practically been the highlight feature of the Google Pixel lineup, and often the saving grace for devices that otherwise would have been mediocre experiences. For the Google Pixel 4 and the Google Pixel 4 XL, Google Camera enables features like Astrophotography mode: a dedicated photo mode that takes very long exposure shots and employs Google's new Night Sight sky segmentation and optimization algorithms to allow the smartphone to capture decent photos of the starry sky, a feat that has otherwise remained very difficult to achieve for other OEMs and their flagships. Long exposure shots are also employed to take creative Light Painting photos: photos where the light source moves during a long exposure shot to emulate a "drawing" effect with the light. As it turns out, Google Camera's Astrophotography mode can also be leveraged to achieve great results with Light Painting photos, as made possible by this Google Camera mod for Pixel devices.

Google Camera PX is a mod for Google Pixel devices and is a result of a collaborative effort between XDA Senior Member cstark27, XDA Senior Member back.rider555, and XDA Senior Member johngalt1. We have talked about this Google Camera mod before, as it enables Astrophotography, Super Res Zoom, and other features on older Pixel devices while enabling features such as 16x Zoom on current-generation Pixel devices. Camera PX has now been updated to a new version, and the highlighting change for this update is the introduction of manual/forced Astrophotography mode and the introduction of a Light Painting mode.

Astrophotography on the stock, unmodified Google Camera on the Google Pixel 4 only activates when you are pointing at the night sky, and are using a tripod to eliminate any possibility of hand movement. As such, Astrophotography mode has some strict parameters for activation. And while the results are amazing for a smartphone, some more flexibility would certainly be appreciated by users. In the example showcased above, the photographer had to be very creative to enable the mode, which would not always be a viable option.

Google Camera Mods -- XDA Subforum

Google Camera PX thus adds a button, allowing users to manually enter or force Astrophotography mode on Pixel devices. The mod also adds another button for a Light Painting mode, which is essentially a tweak applied to the Astrophotography mode to optimize it for light painting shots. You no longer have to fight the app to enable these modes, though it is still recommended that you use these while your phone is on a tripod.

Keep in mind that this Google Camera PX mod is only available for the Pixel devices, so please do not trouble the developers enquiring whether it will be available for other non-Pixel devices. Astrophotography mode is only officially available with stock Google Camera v7 and above on the Google Pixel 4 and Pixel 4 XL, Google Pixel 3 and Pixel 3 XL, and Google Pixel 3a and Pixel 3a XL, though this mod also enables it for the Pixel 2 and Pixel 2 XL and the original Pixel and Pixel XL.

For the complete list of features this mod enables across all Pixel devices, refer to the chart below. "Default" means that the stock Google Camera app already had the feature for the device, "Y"/"OK" means that this mod added the feature to the device, and "N/A"/"Disabled" means that the feature could not be enabled for the listed device, either because of unsolved crashes, missing hardware, or messing up a fundamental function.

You can download Google Camera PX v4.0 from the forum post linked below:

Download Camera PX v4.0 Google Camera mod for Google Pixel lineup

If you don’t own a Pixel, this port will not work just yet. Please do not disturb the developers for supporting non-Pixel devices.