“Papa, FPS is about capturing and also projecting or viewing speed. So the higher the FPS, the higher the number of frames per second. And the higher it is, the more difficult it will be to differentiate between two consecutive frames, right?” Raju asked his father.
“Yes, Raju, two consecutive frames will be very similar to one another. Speeds of more than 60 FPS are used in action scene captures or in sports like races where a hundredth of a second or a thousandth of a second also makes a difference between winner and loser. We are now used to watching slow-motion replays of special moments in almost all sports such as cricket, football, hockey, tennis, etc. Some decisions which are not possible to be taken by relying on the ability or capability of the human eye are taken based on camera captures. We find it used in reviews taken by players in various games,” said his father.
“Yes, when these games are telecast, the original and slow-motion playback is shown to the audience. And it’s then that we realise that what we see when viewing normally isn’t what really happens. Slow-mo reviews are used for line calls in tennis and badminton and also to decide overstepping no-ball in cricket,” Raju said.
“Here the actual filming is done at a higher FPS so that we do not see an image dragging or blurring in the projection at the same speed. Higher capture and projection speeds give a smoother viewing. It provides a good continuous picture quality in slow motion as well. In the various sports, you mentioned it is used in making the right decisions. Today the capture at high speeds is used in the analysis of body motions in sports. Like in athletics where coaches study the body movements and suggest changes to improve the performance. We hear some bowlers change their bowling action after their arm movements are analysed by their coaches or experts. Scientists use these high-speed, high-resolution captures to study the patterns of the explosions of high capacity detonating devices. They are also used in troubleshooting problems in high-speed automatic machines in the industry. In addition, to capture a longer duration pattern one can make use of time-lapse imaging. Here, the camera is set at one location and pictures are captured at slower speeds such as one image per minute or per a set time interval or more. You can take one frame with a pre-decided time gap and when you run these videos you will see it as if you are running a fast forward, but will be able to appreciate the changes that take place during the process that is captured, for example, the movement of a star in the night sky, the blooming of a flower, the completion of a construction site or the germination of a seed into a plant,” his father explained.
“It is so interesting, papa!” said Raju, excited. “I will now take videos at 24, 30 and 60 FPS on my mobile phone and see how they run in a slow-mo setting,” he declared.
“Remember, Raju, at a higher FPS, the size of the video will also be larger,” cautioned his father.
(Writer is a mechanical engineer and runs a hands-on science activity centre at Margao)