The role of video analysis in self improvement

August 4th, 2008 | Quintic Video Software

The commoditization of hardware has put digital movie-making within the grasp of everyone.

Consultancies such as Quintic specialize in capturing action images, and – with a combination of biomechanical knowledge and specifically developed software – clearly show how athletic performance can be optimized and risk of injury minimized.

But specifically how one can use this for best effect is something that not everyone appreciates. Humans have quite slow vision. The human eye can only separate a maximum of ten or twelve images per second. There are even some suggestions amongst scientists that events lasting less than a quarter of a second cannot usually be seen clearly, if at all.

Video cameras create the illusion of motion by ‘tricking’ the human eye. Video cameras play 25 flashing still pictures each second. As the eye cannot separate those pictures, we get the feeling of continuous movement. The use of a video camera is a very effective tool to help you improve sporting technique. Quintic video analysis software enables video capture at 25, 50 and 100fps. At 100fps each still image is 10ms apart, capable of capturing even the fastest of human movement. Add a second video camera, and the benefits of video have just doubled!

More and more athletes, coaches, scientists are using video feedback as a coaching aid. Video can very quickly help athletes to understand the basic fundamentals of a specific movement. Providing athletes with immediate performance feedback via Quintic video software is a very powerful analysis tool… the images are used to assist coaches in their task, as the athlete’s performance can be repeated afterwards and slowed down during critical phases.

By comparing performances of previous movements, or even other athletes, Quintic software enables you to compare video images via the computer screen. Differences between the techniques can be identified (competition vs. training) and this information made available immediately to the athlete. The coach and the athlete can discuss what they see and plan a strategy for improvement, then repeat the process. How the feedback is presented to the athlete when using Quintic is highly dependent upon the skill of the coach or analyst.

By studying your technique in depth, (frame-by-frame), you can start to build a picture of what you’re trying to achieve. Seeing an improvement can boost your confidence. Normally it’s difficult to correct a fault, even if you know what you should be doing. This is because you don’t normally see yourself in action. You can learn a great deal from studying your own technique on video. The benefits of video apply to all levels of performance, from the beginner to the professional golfer.

Some simple tips will greatly enhance the value of your images… There are four basic operations, which can significantly influence the use of cameras and the quality of images:

· zoom
· focus
· iris
· shutter speed

Zoom
During set-up of your camera, it is important to be at right angles, or 90 degrees to the action. The zoom function in the camera changes the picture size and allows you to stand much further back from the action. It is important that the athlete is as large as possible in the camera view. The zoom allows you to have all the details of the performance on the camera, with the view restricted to show only the golfer and nothing else if possible.

Focus
The camera should be set up so that the entire body is contained within each frame. The correct distance between the camera and subject should be recorded, to allow comparisons in the future (Typically 8-10metres). Set the camera to automatic focus. Data collected using Quintic Biomechanics must have a repeatable and consistent set-up protocol. This will ensure the numeric & graphical representation of variables such as speed, distance, acceleration are accurate. Quintic also accounts for any Parallax error values during the calibration of any particular video.

However, if using a panning or moving camera often a manual focus will ensure correct images are recorded. Auto focus constantly checks and focuses based on what is at the centre of the picture. This, though, is not always practical when videotaping athletes. By learning to use manual focus, you can avoid this problem. Manual focus is set for a certain distance (you do not need to know the distance) and anything that distance away from the camera is in focus. This is another reason for you to stand far away from the athlete (and use the zoom function).

A good hint for manual focusing from a long distance is that you zoom in as close as possible, focus your camera using something like the text on an athlete’s clothing and then zoom out to a desired level so that the whole athlete can be seen in the picture. The image stays focused as zoom and focus are independent of each other.

Iris:
The iris is the function in your camera, which allows the light come into the camera through the lens. Many cameras have this only as an auto function and so you may not be able to change it. In any case, auto iris is not such a bad thing as the lighting conditions could change during the session, as happens when clouds go in the front of the sun. If you have a camera with a manual iris option, then you can test out its influence on the picture quality. Obviously, more light (smaller iris number) makes your picture brighter (but can also make it too bright), while closing the iris makes the picture darker.

Shutter Speed:
Shutter speed options are essential for good quality video taping of athletics performance, particularly when the speeds are fast… In a normal situation, the picture is taken over 0.04 seconds (25 pictures in a second). During even that short time, however, an athlete can move a great deal and thus you see a blurred image in your slow motion tape (like TV slow motion repetitions of a tennis ball in a close line call – often you do not really see the ball at all, just a trace of blurred ball images). Shutter speed allows you to reduce the time over which the individual picture is taken. The majority of camcorders today have automatic settings for various filming projects (refer to manufacture’s guidelines). However, the sports setting – typically a picture of a golfer or runner will provide you with the highest shutter speed setting.

Note: That does not allow you to take any more pictures: there are still only 25 / 50 or 100 fps frames per second (as this is pre-determined by the camera and computer software), but each picture is taken over a shorter period of time. A shutter speed of 1/500s means that each picture is taken over a time frame of 0.002s. The down side of increasing the shutter speed is that you need much more light. This is not usually a problem outdoors, and it is recommended to use at least 1/1000s shutter speed for athletics movement if possible, shutter speeds of 1/10,000 can be used for particular sharp and clear images. However, sometimes when filming indoors you need to compromise and use a lower shutter speed. Additional lighting may well be required.
Quintic would recommend you to make a verbal report to the camera after each shot, throw, jump… for example; commenting on the flight, distance, result… Without this information, the subsequent viewing of the tape will not give the best possible information.
Finally, remember that the videotapes always rewind slightly at the end of the recording, so be careful not to cut away the end of the performance when you stop the recording. Film a few seconds prior to and after the actual performance. This also makes easier viewing, as there are distinct sequences on the tape.

Ensure that the camera is a 3CCD – CCD stands for Charged Couple Device – it’s the device that colours the pixels (little dots on your screen – comes from the words ‘picture element’). The majority of cameras only have one CCD using a filter to split the colours to RGB (Red Green and Blue). However a 3CCD camera boasts a CCD for each colour, resulting in better picture quality as the colours are more defined and accurate.

For further details please visit www.quintic.com

Warning: require(/home/quintics/public_html/wp-content/themes/new_theme/comments.php) [function.require]: failed to open stream: Permission denied in /home/quintics/public_html/wp-includes/comment-template.php on line 889

Fatal error: require() [function.require]: Failed opening required '/home/quintics/public_html/wp-content/themes/new_theme/comments.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/quintics/public_html/wp-includes/comment-template.php on line 889