Video recording

Video recording: it plays a crucial role in biomechanics analysis. It makes possible to record human motions to replay pictures. To use the most appropriate camera is indispensable so that pictures/frames would be suitable for the process of analyses. The characteristics of a camera which can be used for motion analysis are the followings:

• motions should be recorded with frame rate meaning the number of frames per second (fps),
• appropriate exposure time is needed (shutter speed képlet ) to have sharp recordings/shootings,
• small/low angle lens are suitable for sharp recordings, therefore focus length is important as it can show the distance between lens and “sensitive layer”  képlet hiányzik; as well as an aperture which regulates the amount of light entering,
• it should be able to enlarge brightness electronically (ISO) although if it is often used it may result “noisy” frames/pictures.

It is suggested that recording should be done with high frame rate. To have sharp frames exposition time should be shorter. Camera should be placed far away from the recorded motions thus distortions at the edge of lens may not appear, screen will be in small angle and the change of angular movement is insignificant. If zoom must be used it is not allowed to change its angle. The enough quantity of light is indispensable which can be provided with the aperture. It is a hole within a lens through which light travels into the camera body. ISO setting must be changed to take better photographs. If there is not enough light it is worth using either a halogen or HMI bulb (it does not vibrate). Camera tripod must be used and lens should be lifted up to the centre of gravity of the individual doing motions. Frame of reference must be used which is perpendicular to the camera, this provides the extent of the movement. The recorded motion can be in the background or a fix point can be also used with the same zoom. So the frame of reference will not be present but the fix point will give us the proper rate of comparison. Individuals whose motions are recorded are suggested using markers on, for example, on joints, bones and muscle adhesions. The colours of these markers must contrast with the environment. Computer systems make digitizing much easier. There are motion sensors in laboratory conditions which convert motions into signals while data are processed by a computer.