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Live HDR+ and Dual Exposure Controls on Pixel 4 and 4a

Monday, August 3, 2020

Posted by Jiawen Chen and Sam Hasinoff, Software Engineers, Google ResearchHigh dynamic range (HDR) imagingengine behind HDR imagingHDR+ burst photographyLive HDR+dual exposure controls

Live HDR+ on Pixel 4 and 4a helps the user compose their shot with a WYSIWYG viewfinder that closely resembles the final result. You can see individual images here. Photos courtesy of Florian Kainz.

The HDR+ Lookreduce noise

Different ways to tone-map a linear RGB image. (a) The original, “un-tone-mapped” image. (b) Global curve optimizing for the sky. (c) Global curve optimizing for the subject. (d) HDR+, which preserves details everywhere. In the 2D histogram, brighter areas indicate where more pixels of a given input brightness are mapped to the same output. The overlapping shapes show that the relationship cannot be modeled using a single curve. Photo courtesy of Nicholas Wilson.

localLocal Curve Approximation for Live HDR+

(a) Input and HDR+ result. (b) The effect of HDR+ on a small patch (red) is approximately a smooth curve. (c) The relationship is nearly identical for the nearby blue patch. (d) However, if the patch is too big, a single curve will no longer provide a good fit.

GPUsHDRnetdeep neural network

HDRnet vs. HDR+ on a challenging scene with extreme brights and darks. The results are very similar at viewfinder resolution. Photo courtesy of Nicholas Wilson.

Dual Exposure Controlsexposure compensation

Screen capture of dual exposure controls in action on an outdoor HDR scene with HDR+ results below. You can see individual images here. Photos courtesy of Florian Kainz.

Different renditions using Dual Exposure Controls. You can see individual images here. Photo credits: Jiawen Chen, Florian Kainz, Alexander Schiffhauer.

AcknowledgementsLive HDR+ and Dual Exposure Controls is the result of a collaboration between Google Research, Android, Hardware, and UX Design teams. Key contributors include: Francois Bleibel, Sean Callanan, Yulun Chang, Eric Chen, Michelle Chen, Kourosh Derakshan, Ryan Geiss, Zhijun He, Joy Hsu, Liz Koh, Marc Levoy, Chia-Kai Liang, Diane Liang, Timothy Lin, Gaurav Malik, Hossein Mohtasham, Nandini Mukherjee, Sushil Nath, Gabriel Nava, Karl Rasche, YiChang Shih, Daniel Solomon, Gary Sun, Kelly Tsai, Sung-fang Tsai, Ted Tsai, Ruben Velarde, Lida Wang, Tianfan Xue, Junlan Yang.