server because there is no separate plug-in
available (yet) that can adjust focus in Lytro
images.
Our lab tests confirmed that the Lytro’s
images are – to put it politely – not particularly
high quality. We measured resolution of 215
vertical line pairs, which represents only 57
percent of the theoretical maximum.
However, the camera’s signal-to-noise ratio
and visual noise value were comparable with
those of some current compact cameras.
Automatic white balance was extremely poor,
and the Lytro produced very noisy images in
artificial light. Images shot at telephoto focal
lengths show a distinct loss of sharpness,
probably due to the camera’s limited overall
image resolution. This is another aspect of the
Lytro experience that is simply not as good as
the results produced by conventional
compact cameras.Industrial Light Field Cameras
The purely consumer-oriented Lytro isn’t the
only commercial application of light field
technology available. The Raytrix company in
Germany (www.raytrix.de) has been
marketing 3D light field camera systems for
industrial measuring and photographic
purposes since 2009.
Depending on which software you use to
view it, light field data captured with a Raytrix
camera can be displayed with all or just some
of the captured planes in focus. This gives the
user access to visual data relating to precisely
definable levels within an object, which
can be used for quality control during
manufacturing processes or for complex face
recognition applications, and can also be
used to build 3D models of photographed
objects.
The R5 is the simplest Raytrix camera. It has
an effective resolution of 1.2 megapixels and
captures data on more than 30 levels, while
the top-of-the-range R291 has seven
megapixels of resolution and is capable of
capturing up to 200 levels of 3D data. The
exact distances between these ‘layers’ is
determined by the type of microlenses you
choose when configuring the camera’s
hardware during manufacture.
Raytrix cameras are designed primarily for
industrial use and are built to custom
specifications that depend on the customer’s
individual requirements. You can choose
from a range of lenses and software to
match. The computer you use to analyze and
display the resulting data needs to have a lot
of graphic power (a fast NVIDIA card, for
example) and CUDA support. Prices for such
high-end technology start at around e8,500
(US$10,500) for camera, software andcomputer. The R29 starts at around e20,000
(US$25,000) for the camera unit alone.
The Institute of Computer Graphics at the
Johannes Kepler University in Linz (Austria) is
currently using a Raytrix R11C to develop a
light field panorama application. The system
is still in the early stages of development,
although the team has already produced light
field panorama images with an effective
resolution of 22 megapixels (17 885x1 275
pixels). More details and sample images are
available at the Raytrix website. Raytrix
cameras are also used to produce 3D data for
use in the automotive industry.
Such highly specialized cameras are not at
all suitable for taking spur-of-the-moment
holiday snaps. Just as the first usable digital
cameras were clumsy and far too expensive
for everyday use, practical applications for
light field photography are still very much in
their infancy, and the companies and
products introduced here are not the only
ones that are busy harnessing this fascinating
technology. Who knows – maybe in a few
years’ time, every smartphone will have a
built-in light field cameraˇ...Conclusion
If measured against conventional yardsticks
such as resolution or contrast ratios, the Lytro
is sure to disappoint, but those criteria don’t
do justice to what is really fascinating about
this technology. Its real strength lies in its
sensational ability to change the point of
focus in an image at will. This amazing
functionality enables the photographer to
focus attention on a particular detail and the
viewer to ‘customize’ the current view of an
image. The Lytro proves the viability of
consumer applications for a technology that
has, up to now, been the preserve of research
labs and industrial specialists. Once the initial
buzz has worn off, the current Lytro will
probably not be seen as much more than
an interesting toy. However, in the long term,
its appearance might just prove to be a
seminal moment in the history of digital
photography. (anm)References
[1]ˇRen Ng: Digital Light Field Photography,
Stanford University 2006, http://www.lytro.com/
renng-thesis.pdf
[2]ˇhttp://graphics.stanford.edu/projects/
lightfield/
[3]ˇRen Ng et al.: Light Field Photography
with a Handheld Plenoptic Camera,
http://graphics.stanford.edu/papers/
lfcamera/lfcamera-150dpi.pdf cLight Field Photography | Industrial Applications
You can alter the point of focus in
‘normal’ and macro light field images
with a single mouse click. Generally
speaking, the Lytro produces well-defined
close-up images, but its telephoto images
are not particularly sharp.