Pixels in Space!

The camera has always been one of the standout features of Google’s Pixel phones. Every few months, the app is updated with new features. As the basics of everyday photo taking were already covered, some of these additions are rather niche. Portrait mode was nice to have, giving a soft bokeh blur to the background, but it still struggles with curly hair. Time Lapse mode is neat, but not something I’ve really found a use for. Night Sight mode was a recent example of a feature with more widespread appeal, providing a huge leap in quality for low-light photos. I can’t however imagine a lot of people would ever consider using their phone to take pictures of the night sky…

Origins of Astrophotography Mode

From what I can tell, it started with a 2017 experiment outlined by Florian Kainz on Google’s AI Blog that involved building on the HDR+ exposure stacking function which itself debuted back in the time of the Nexus 5 (2013). In his post, Kainz concluded that the photos required “a lot of careful post-processing on a desktop computer”, but that “with the right software a phone should be able to process the images internally … it might be possible to do point-and-shoot photography in very low light conditions.”

Two and a half years later, Google has figured out the “right software” part, and released it as Astrophotography mode (henceforth Astro mode) on the Pixel 4. Thankfully it’s also available to the Pixel 3 by downloading Google Camera app V7.1 or later.

Long Exposures for Low Light

But what would happen if you tried Astro mode indoors? Could it perform similar magic to make very dark scenes visible? Apparently so:

These shots of a bookshelf above my TV were taken in an extremely dark room, lit only by a single shaded bulb two rooms away. The standard HDR+ mode didn’t have anywhere near enough light to produce more than a black image. Night Sight (on the left) managed a bit better, but the resulting image is extremely noisy and unclear. You can’t even make out the grey right edge of the TV against the black panel that it’s mounted on. The Astro shot on the other hand is smooth where it should be (the shadow gradients on the ceiling), yet sharp enough to read the book titles. Judged by usual rules it’s not a good photo, but considering the light available and the fact that it was taken on a phone with a 1/2.55″ (9.9mm) sensor, it’s bordering on incredible. See the cropped zoom for more detail:

Long Exposures for Fun

Astro mode can’t currently be triggered manually – it relies on the camera being set to Night Sight, remaining completely still for a few seconds, and there being a very low amount of light*. In practice this means using a tripod or resting the phone against something solid. This limits the creative possibilities somewhat, but there is a workaround. If you cover the lens once the phone is still, Astro mode will be enabled. You can then hit the shutter and immediately uncover the lens. On the Pixel 3, this usually gives you a 65 second exposure to play with. It’s also possible to end the exposure before this by hitting the shutter icon again.

*Using a modified version of the Google Camera app, it’s now possible to manually trigger astro and light painting modes. See the end of this article for more info.

Above is my first attempt at tricking the camera into Astro mode. The pink smudge at the top-right is my thumb as I removed it. Unlike a long exposure shot with a DSLR, the buildings are quite sharp, and light trails smooth. It’s an odd hybrid of short and long exposures.

The Sky at Night

Back in its native environment, Astro mode can capture incredible numbers of stars in a dark sky. The following were taken in a reasonably dark location in Donnington, on the edge of Newbury. There were street lamps nearby, but with careful adjustment of the levels in Photoshop (or even in the basic editing tools built in to Google Photos), the sky can be reduced to an inky black, penetrated by the light from thousands of distant suns.

Update (25-Nov-2019)

9to5google has an article about a modified version of the Google Camera app called Camera PX, which enables toggles for astro mode and light painting mode, along with various other tweaks and additional settings. This is available to be sideloaded on any Pixel phone, although only more recent models will have all the options available:

• Camera PX thread on XDA
• Download Camera PX on APKMirror