Illustrating Motion with DLP Photography

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.


"Illustrating motion through DLP Photography"
S.J. Koppal and S.G Narasimhan
IEEE International Workshop on Projector-Camera Systems (PROCAMS),
June 2009.


Presentation [PPT]


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.
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.
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.
Summaries of real time scenes:
We combine photographs containing the color-wheel effect using shape-time photography to summarize the dynamic event.


(Video Result Playlist)
PROCAMS 2009 Video (use Windows Media Player):
This video is a compilation of the main results of this project (4 MB).
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.
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.