1. Motion blur in some pictures are important because when there is motion blur, you can tell when something is moving. If there was a car moving with no moton blur, you wouldnt be able to tell if it was moving or not. 2. I feel as if intentional motion blur is most effective and important because it captures the motion and really shows the moving part of the image. The whole backround of an image could be clear and only the moving portion would be blurry, capturing the motion in the image better in comparison to an accidental blur. 3. To decrease the brightness of the subject, you should lower the ISO.