# How to measure the speed of ball from a video or a set of pictures? [closed]

Suppose a camera and the need to measure the speed of a ball such as a tennis ball. Usually, the speed of ball is measured with Doppler effect where the pulse difference reveals the speed. Now I want to measure the speed of the ball from the images with Mathematica. You can suppose 1/30 sec shutter speed.

How would you measure the largest speed of the ball in Mathematica?

Different Methods

I. Image Difference method

Shoot two pictures in 1 second interval. From the difference of images, you get the length travelled. By the $\Delta t$ and $\Delta l$ you get the speed over that range. Simply use Mathematica's Image Difference here.

II. Long shutter time method with a glow ball

Like in light-painting, use a fire-ball or glow-ball or light-ball. Now get one photo with long shutter time in a black room with only ball glowing. Measure the length of the glow over certain time. Programmatically, the task is to measure the length of the flight path.

III. Motion blur method

A camera experiences a motion blur with a fast ball. An user suggested a motion-blur method but I could not understand it. Perhaps just sharpen and use the method I above. Two test images are here and here where the ball has travelled about 4 meters in 23 frames.

IV. Some other method to get the speed of ball from images or a video?

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## closed as off-topic by m_goldberg, Pickett, Rahul Narain, Jens, KubaApr 24 at 5:09

• The question does not concern the technical computing software Mathematica by Wolfram Research. Please see the help center to find out about the topics that can be asked here.
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The shutter speed is relevant for the single image methods, but you will also to know a lot about the characteristics of the shutter mechanism. For working with multiple images, you will need to have a very accurate time code for each image because the intervalometer delta-t is usually not trustworthy. –  m_goldberg Apr 24 at 1:51
This question is off-topic because it is about the design of an experiment to capture data for later processing and not about using Mathematica to do the processing. –  m_goldberg Apr 24 at 1:58