Rain produces sharp intensity fluctuations in images and videos, which degrade the performance of outdoor vision systems. These intensity fluctuations depend on various factors, such as, the camera parameters, the properties of rain and the brightness of the scene. It turns out that the properties of rain – its small drop size, high velocity and low density – make its visibility strongly dependent on camera parameters such as exposure time and depth of field. In this project, we demonstrate how these parameters can be selected so as to reduce or even remove the effects of rain without altering the appearance of the scene.The proposed method serves to make vision algorithms more robust to detect rain without any need for post-processing. In addition, it can be used to control the visual effects of rain during the filming of movies. Conversely, the parameters of a camera can also be set to enhance the visual effects of rain. This can be used to develop an inexpensive and portable camera-based rain gauge that provides instantaneous rain-rate measurements.
Rain Visibility and Camera Parameters:
The visibility of rain is strongly dependent on camera parameters such as exposure time, F-number and distance of the focused plane. This graph shows how the visibility of rain is affected by these camera parameters.
Rain Removal as a Camera Feature:
Controlling the visibility of rain by selecting camera parameters does not require any post-processing and hence can be easily incorporated in commercial cameras for reducing or enhancing the effects of rain. Here we show a simple lookup table that can be used to set the optimal parameters for rain reduction for a Canon XL1 video camera.
ICCV 2005 Video:
This video shows the results of rain reduction by camera parameter selection for several rain scenarios. (With narration)