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CAMERAS | 
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Digital Video Cameras for use with Video Analysis Software |
How much is a decent camera going to cost me?
The PAL video format is a standardised European 'norm', therefore it doesn't matter whether you buy a £500 or a £1200 DV camera you will still get the same number of frames per second and the same size of image.
PAL captures 50 images per second, 25 odd and 25 even fields, they are then interlaced to produce 25 images per second. Just to give you an idea, a well train human eye can perform at 7 frames per second.
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Standard digital video cameras compress the video stream with a MJPEG algorithm, band width is approx. 3.5 MB/s (=26 Mbit/s). They can transfer compressed stream via firewire (IEEE 1394) directly to your computer. Image size is 720 x 576 (PAL).
When purchasing a DV camera for motion analysis, try not to get involved with useless features like the amount of 'mega pixels' it has for still photography - unless of course you wish to take holiday snaps. Many other features are simply for home video use and therefore not applicable for motion analysis.
So how can you make a real difference with your video recordings?
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.
Lighting - if your filming predominately indoors the light source must be able to provide a clean look on the subject - we use Ceramic Metal Halide (CMB) bulbs as they are a 'clean' source of light. They are also fantastic at reducing shadows when used as a filler light, as they do not have a sharp edge nor focused beam.
Calibration sheets are a basic requirement to achieve an optimal positioning of your cameras. The sheets are located behind (and beside) the subject (treadmill), and thus enable an exact horizontal and vertical positioning of the camera. In addition, the monochromatic colour offers a good contrast to the skin and the skin markings of the athlete. The calibration sheets are available on a 5mm plastic board with surface protection that is matt finished to prevent unnecessary reflection or shadows.
Use camera mounts - not tripods. Once you have used a professional mount you will never go back. This is important when running consecutive images in concurrent analysis - how can you be accurate with your analysis is based on two view from differing positions.
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