Bright whites, yellow suns, and deep blacks are the goal, not the cure, when it comes to high dynamic range (HDR) capture and
viewing of premium content. After all, as we live
through the dog days of summer here in North
America, don’t we want our captured memories to be equally as brilliant or as dark as the
From pinholes to subpixels, or from 8-bit to
12-bit, the quest for HDR continues to outpace
the quest for virtual reality video or even 4K
In early 2017, we saw several competing HDR
options emerge, with one using 10-bit color samples and another using 12-bit color sampling.
To understand why the extra bits matter, we
have to harken back to the days when some of
us spent parts of the summer in a darkroom,
processing 35mm film rolls or even photosensitive paper through a series of trays filled with
various chemicals from household names like
Fuji or Kodak.
Images captured on film, either through a pinhole or a more traditional multi-aperture-based
camera lens, use the terminology of a “stop.” A
stop is essentially a click-point on the camera
lens, with each stop designating a different aperture. In film school, we were taught to differentiate between f-stops and t-stops, but outside
the realm of cinema, the use of the term “stop”
refers to an f-stop.
The aperture itself determines how deep or
shallow the focus will be, which is where we get
the terminology for depth of field that’s now being tossed about for consumer smartphones. The
Apple iPhone 7 “depth effect” feature makes use
of two lenses to create a digital version of depth
In addition, the aperture setting had to be
balanced with the sensitivity of the 35mm film
stock. If too much light reached the film, the image would be washed out (eventually going to all
black on the negative, which rendered all white
on the printing)—but if too little light reached
the film, the image would be grainy and dark.
Black-and-white photography, from the mas-
ters like Ansel Adams to the more mundane In-
stamatic 110 cartridge camera I had as a child,
is based around the balance of these light and
dark areas. While color adds an extra dimen-
sion, even good color photographs are lessons
in contrasting darks and lights.
Different film stock had different tolerances
or latitudes for these dark and light areas, and
the ability to have a wide latitude meant the
ability to capture bright whites and dark blacks,
rather than just 50 or more shades of gray.
The move to digital capture meant a more
muted capture, since most digital sensors had
a very limited latitude. That has improved over
the past few years, though, with digital sensors
beginning to reach a range of latitude that rivals
film. Which brings us back around to HDR and
the reason that the bits are so important. The
number of bits in the bit-depth for digital capture equates to the number of stops or range of
latitude for older film cameras.
An 8-bit capture device offers about six stops
of latitude, but a 10-bit capture device is capable
of almost three times the range of latitude, at
almost 18 stops. If more bits are added—going
up to the 12-bit offerings now on the marketplace for still image capture and some limited
video capture—the range of latitude increases
Unfortunately, just because a camera can
capture in the more latitude-friendly 10-bit
mode, the image quality is lost when a video
is viewed on a playback device that only displays eight bits of color depth. And that’s even
assuming that the stream is being delivered in
HDR-friendly 10-bit or 12-bit options, because
these higher bit-depth options equate to significantly higher data rates.
Movie cineplexes understand this, and focus
some of their efforts on eking out much higher
dynamic ranges than the typical home HD set.
But the home front is improving, thanks to efforts to introduce various versions of HDR into
consumer flat panels.
At the IBC show in Amsterdam in September, expect to see several more HDR choices
for both streaming and viewing. In the meantime, enjoy the summertime blacks in the world
Tim Siglin is a streaming industry veteran and longtime
contributing editor to Streaming Media magazine.
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