The document discusses the development of a True HDR app for iPhone. It captures scenes that the human eye can see but most cameras cannot by computationally merging multiple exposures of the same scene. Key challenges included automatically aligning photos with different exposures, merging them naturally without artifacts, managing memory constraints on mobile, and processing images quickly. While popular for a time, updates were rejected by Apple for 8 months, though it provided lessons learned.

1. Developing the
“True HDR” app
for iPhone

2. 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...

3. 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.

4. Capture what your eyes see, via
computational means

5. Capture what your eyes see, via
computational means

6. 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.

7. 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

8. The Ups and Downs of App
Development
Highlights
● 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

9. Contact me:
Yuanzhen Li
yzli@csail.mit.edu
Interested in computational photo
app projects?