Creating a natural-illumination invariant image of a moving scene

Many image processing applications could potentially be simplified or improved if the scene lighting is invariant. A flash can provide consistent illumination in an image, but the flash intensity required in sunlight is impractical. An image of the scene taken without the flash can be subtracted to leave only the flash illuminated image if there is no motion in the scene, greatly reducing the flash intensity required. If there is motion, the image changes due to motion can be corrected in the no-flash image before being subtracted from the flash image. The proposed ratio based estimation provides a technique for this. Three different image sources, video, rendered video and shifted still images are used to quantify the advantage of ratio based estimation. The estimate error is shown to be reduced by 49% using ratio-based estimation compared to subtraction of a previous image.