Motion Blur Length

This formula says that motion blur is the distance a subject travels while the camera shutter is open. If something moves at a steady speed, then distance = speed × time, so the length of the blur on the image follows the same idea. A longer shutter time or a faster subject makes the streak longer; a shorter shutter time or slower motion makes it shorter.

Use this when estimating how much a moving object will smear in a photo, such as a runner, car, bicycle wheel, or panning shot. It is especially helpful for choosing shutter speed when you want either to freeze motion or deliberately show motion blur.

• Using the shutter speed value directly without converting it to seconds
• Forgetting that the formula gives distance moved during exposure, not the blur seen on the sensor in pixels
• Assuming the subject speed changes during the exposure when this simple formula only works for constant speed