Whether taking photos recreationally or professionally, photographers understandably want their snapshots to appear sharp and clear. Image clarity is dependent on exposure time, or the amount of time that a camera's sensor is exposed to light while a photograph is being taken. During this period, the shutter opens and the camera counts the number of photons emitted by the subject.
In a paper publishing this week in the SIAM Journal on Imaging Sciences , Tendero and Morel develop a closed formula meant to reduce motion blur.
Flutter shutter causes a camera's shutter to open and close repeatedly based on a pseudo-random binary sequence, which increases exposure time. A shutter sequence, called a flutter shutter code, then reveals intervals where the photon flow experiences interruption. A successful flutter shutter code guarantees an invertible motion blur kernel that reverses severe blur, resulting from arbitrarily high velocities. Yet there is a limit: when the velocity of the camera or scene is constant, a flutter shutter is incapable of gaining more than a 1.17 factor in terms of root mean square error (RMSE), when compared to an optimal snapshot. This term is respectable, but a higher factor would be more sensitive and thus yield a clearer image.
While past studies have addressed ways to achieve invertible motion blur, most involve applications that are more complicated than the original flutter shutter. Tendero and Morel present a new closed formula that allows computation of optimal codes for any probability density of the expected scene velocities. This formula links optimal flutter shutter codes and velocity distributions.
The authors' formula makes it possible to associate optimal velocity distribution with an existing flutter shutter code. Using their stochastic velocity model, they surpass the previously-established 1.17 bound gain for known velocities, provided that the scene's velocity is known or able to be learned. The resulting flutter shutter code is invertible for all velocities.
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Source Article: A Theory of Optimal Flutter Shutter For Probabilistic Velocity Models
SIAM Journal on Imaging Sciences , (to be published)
The paper will publish online March 23rd. Email sorg@siam.org to obtain an advance copy of the paper.
SIAM Journal on Imaging Sciences