Developing the “True HDR” app

for iPhone

Why HDR?

Often, you see a beautiful scene but you cannot capture it on camera.

You get the sky but the rest of the picture is too dark...

Why HDR?

Or, you get the shadows but the sky is washed out.

Your eyes perceive high dynamic range but most cameras have low dynamic range.

Capture what your eyes see, via computational means

Capture what your eyes see, via computational means

A bit of history● Released in 2009 after Apple introduced the 3GS with “auto-focus”

feature.

● At the time, there were several apps with “HDR” in their names but all they did was single-image contrast enhancement.

● Initially version was low-resolution (1 MP); current version supports up to 19 MP.

● Apple’s introduction of built-in HDR in 2010 didn’t kill the app. Not all HDR’s are created equal; many like our results better.

Challenges

● Automatically aligning photos with drastically different exposures

● The merge should be as natural-looking as possible. We don’t want halo artifacts.

● Image processing can need a LOT of memory but memory is a prized resource on mobile

● Doing things fast

The Ups and Downs of App DevelopmentHighlights● Appreciative users● Was #1 in Japan and #3 in the US, for a short time● Was inaugural member of Apple’s “App Store Hall of Fame”

Setbacks● 8-month period when updates kept getting rejected by Apple

Lessons & Anecdotes

Contact me:Yuanzhen Liyzli@csail.mit.edu

Interested in computational photo app projects?