The Constraints
Gcam project had us impressed with the HDR+ mode on the Pixel and the Nexus phones which allowed users to take photos at the low-level light by burst shooting ten short exposure and then combining them into a single image. Once the automatic post-processing is done the grains and other noises in the background are drastically reduced. The SeeTheDark app which was presented at the ICCV 2015 Extreme Imaging Workshop showed us how the smartphone camera can capture images at the extremely low light by accumulating more exposures and ultimately merging them into one. During this process, the image is assumed to be static and any resulting motion is a consequence of camera motion. The app attempts to further reduce the noise by reducing the resolution to 1-Megapixel. In order to maintain the motion blur and other movements below the accepted level, both the HDR+ and the SeeInTheDark must keep the exposure time for individual frames below 1/10 of a second. That being said, if the scene is indeed static, one can simply increase the exposure time to more than a second and ensure that the phone is firmly planted with the help of a tripod or any other support. Focusing on the subject can be a messy affair and according to the Google Engineer turning the focus to infinity should do the trick.
Also Read: We Took Pictures of a Bulb with an iPhone and a Sony A6000… and You Won’t Believe the Results!
The Experiment
In order to achieve the desired results, Florian wrote a “simple” camera app that would allow him to have a manual control over exposure time, ISO and also the focus distance. After pressing the shutter the app is designed to record up to 64 frames and save the frame captured as DNG files which are easy to be post processed.
The app was tested using a Nexus 6P and shots burst of 32 four-second frames at ISO 1600. In order to complete the experiment, Florian further shot another 32 black frames after covering the smartphone camera lens with an opaque tape. The resulting image of the experiment can be seen above. The lantern might seem a little bit overexposed but the rest of the elements is pleasing to look at. For the sake of comparison, you can also see the photo from a hand-held HDR+ shot below.
In the next step, Florian went on to capture a full nighttime landscape along with the brighter stars. In this particular case the subject that is the stars are in motion, while they might appear to be stationary it’s a well-known fact that stars rotate around the celestial poles and while the motion in itself might not be substantial to damage an exposure set over seconds it does show up in the picture wherein the exposure is set to longer duration of time. As you can figure out in the picture below the stars have blurred out.
The blurs or the streaks associated with the stars can be avoided by shifting the original frame and aligning the same with the stars, but this also means that the ground is in motion now and thus appears to be blurred. This situation can be overcome by taking two pictures, one with the ground moving, other with the frame stationary and merging both of them, just like the picture below.
Continuing the experiment with less light
Florian further continued the experiment, this time he used a Pixel and tried capturing scenes with the lesser light. All of the images were shot at 64-frame burst and the resulting photos were looking good.
The picture above is a result of combining 64 two-second exposures taken at ISO 12800 and this did end up well with the visuals of Milky Way. Also clearly visible in the picture are the constellations Scorpius and Sagittarius. That being said Florian says how one could still set the exposure at a relatively higher level and lower the ISO setting in order to reduce the noise significantly and attain a clearer picture.
Moving on to the final part of the challenge the original shot of the San Francisco Golden Gate bridge. The Google engineer retook the shot with the Nexus 6P and the resulting image is surprisingly good. The dynamic range captured eliminates saturation and the colors look to be pleasing as well. The sharpness of the photo is also commendable and its worth mentioning how the quality remains consistent throughout the corner.
In a nutshell, the smartphone camera might not be a direct match to a DSLR but they are right up their alley. A quick look at the samples above will show you how close the results are. That being said the pictures taken on the smartphone camera had to be subjected to several rounds of post processing and in the future maybe a comprehensive post processing software will take care of the needs. Check out the Images in original Resolutions
