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Strobe-light photography
creates beautiful high-frequency effects by capturing multiple object
copies. Single-chip DLP projectors produce a similar effect, with two important
distinctions. Firstly, strobing occurs at different frequencies: at 10000Hz,
due to the DMD chip, and at 120Hz, due to the colorwheel. Secondly, DLP
illumination lacks the perception of ’on-off’ flashing that
characterizes a strobe-light, since these frequencies are beyond human
perception. Deblurring images taken under such strobe-like illumination is
difficult, especially for articulated and deformable objects, since the
deconvolution kernel can be different at each pixel. Instead we process DLP
photographs to create new images that either summarize a dynamic scene or
illustrate its motion. We conclude by discussing the frequencies present in
DLP photographs, comparing them to images taken under skylight and
fluorescent light.
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Publications
"Illustrating
motion through DLP Photography"
S.J. Koppal and S.G Narasimhan
IEEE International Workshop on Projector-Camera Systems (PROCAMS),
June 2009.
[PDF]
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Presentation
Presentation [PPT]
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Pictures
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Input images with DMD effect:
We illuminated very fast
moving scenes (with a speed much greater than 120Hz) under DLP projector illumination.
The DMD chip creates strobing around 10000Hz. These images clearly show
the repeated edges in the balloon and the high-frequency blur in the
sling-shot.
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Summaries of
very fast moving scenes:
We
combine photographs with the DMD high-frequency blur using the method of
shape-time photography previously used in computational photography.
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Input images
with color-wheel effect:
We illuminated
dynamic scenes (with a speed around 120Hz) under DLP projector illumination. Th
color-wheel creates multi-colored strobing at 120Hz. These images clearly
show repeated copies of the ballet dancer and the tabla player.
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Summaries of real time
scenes:
We combine
photographs containing the color-wheel effect using shape-time
photography to summarize the dynamic event.
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Videos
(Video Result Playlist)
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PROCAMS
2009 Video (use Windows Media Player):
This video is a compilation of the main results of this project (4 MB).
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Ballet
Summary Video (use Windows Media Player):
We separate the images from the ballet video into a ‘strobed’
and a ‘non-strobed’ part. We blend the non-strobed (static)
part slower than the strobed part, illustrating the motion.
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Tabla
summary Video (use Windows Media Player):
We
create a video from a series of color images of a tabla players,
separating each into its R, G and B channels. Therefore we create a
grayscale video illustrating the motion.
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