| Planning to pick up a new DV camera that can be | | | | look at the shutter speed and whether it is manually |
| used to film the kids and your Tennis serve too? Then | | | | adjustable. A camera that automatically adjusts its |
| getting the right camera is important to help you obtain | | | | shutter speed to the lighting conditions can make you |
| excellent sports analysis footage and make your video | | | | forget the importance of ensuring good lighting on your |
| analysis of sports performance clearer. We have | | | | subject. |
| picked out some of the most important camera | | | | Resolution |
| specifications for sports analysis and listed them in this | | | | We all know about resolution from high def televisions. |
| article. | | | | High def television can only display those high definition |
| Speed and Size | | | | images if they were recorded by a high definition video |
| Like most sports, a good sports analysis camera | | | | camera. The resolution of a video camera is a |
| needs speed and size. There are a few different | | | | measure of how many pixels our camera sensor has. |
| speed and size measures of a camera and they are | | | | Luckily for us most video camera manufacturers are |
| discussed below. | | | | now making HD cameras with about 1920x1080 pixels |
| Frame Speed | | | | or 2.3 Mega pixels. Of course a higher resolution is |
| Most off the shelf DV cameras have a standard | | | | always better just like it is on our TVs. |
| frame speed of 30 frames per second or fps(NTSC) | | | | Lens Choice |
| in the North America and 25 fps (PAL) in most of the | | | | There are 2 important aspects of a lens for sports |
| rest of world. What this means is that the camera | | | | performance capture, aperture (f-stop) and focal |
| records 30 pictures every second, one picture every | | | | length and optical zoom. |
| 0.03333 seconds. 30 frames per second is the speed | | | | Aperture |
| at which most regular television is recorded and | | | | The aperture or f-stop is a measure of the amount of |
| viewed. When these 30 frames are played back at full | | | | light the lens of the camera will allow through. A lower |
| speed every second, our brain is unable to distinguish | | | | number will allow more light into the camera and a |
| between the individual pictures and we see a flowing | | | | higher number less light. Most DV cameras have |
| video. | | | | f-stops as low as 2.5 which is good enough for sports |
| However, if we want to analyze a tennis serve then | | | | analysis purposes. Once again just like with shutter |
| we need to slow down our video and look at each | | | | speed there is a trade off. A lower f-stop can often |
| one of these 30 frames of every second and this is | | | | result in a lower resolution image. This does not mean |
| where a problem may arise. As the serve is generally | | | | that the cameras sensor has less resolution but that |
| a quick motion, we will probably find that if we only | | | | there is a trade off with lighting and quality. Once again |
| record 30 fps then the arm will look like a blur during | | | | this points to making sure you have a good light |
| the serve motion and we will be unable to analyze it | | | | source for your recordings. With a good light source |
| properly. To solve this problem we can record the | | | | you can use a lower f-stop and therefore obtain a |
| motion at a higher frame rate, say 60 fps and get | | | | better resolution image. |
| double the amount of pictures every second. This will | | | | Focal Length |
| give us more data to analyze and reduce the | | | | The focal length is the distance from the lens to the |
| possibility that the motion will be blurred. | | | | camera's sensor. A smaller focal length means that |
| In general the more frames we can capture per | | | | the camera will capture a wider angle of view and see |
| second the better our analysis can be. Luckily though | | | | more in the frame, while a large focal length allows the |
| there is a limit. In most sports when analyzing the | | | | camera to see more details further away. Focal length |
| human body movement 250 fps is sufficient. If we | | | | and optical zoom therefore are linked. Optical zoom of |
| then want to include say the golf club or tennis racket | | | | course allows us to zoom in or away from an athlete. |
| and analyze its movement, we once again need higher | | | | Most DV cameras come equipped with optical zoom |
| speeds maybe up to 500 fps. | | | | and will read something like 49-735mm, which is the |
| Unfortunately though there are very few off the shelf, | | | | range of focal lengths that can be achieved with this |
| commercial cameras that can record high frame rates. | | | | camera. |
| You can find some cameras that can record 60 fps, | | | | The more optical zoom we have the further away we |
| but if you want to go higher, costs can increase | | | | can be while still recording excellent footage for |
| substantially. We think a 60fps camera is a perfect | | | | analysis. Now its up to us to use that optical zoom |
| start for doing your own analysis. | | | | effectively by positioning our athlete correctly in the |
| Shutter Speed | | | | field of view. Check out for details. |
| We can get away with the usual 30 fps as long as | | | | Also don't get tricked by digital zoom. Digital zoom is |
| we have a high shutter speed. Shutter speed | | | | not our friend and if used can reduce our actual |
| determines exposure time, or how long the cameras | | | | sensor resolution considerably. It is far better to |
| sensor is open to receive light and therefore record | | | | reposition our camera closer to the athlete than make |
| the frame. In sports analysis the higher the shutter | | | | use of digital zoom. |
| speed the less blurred our image will be. However | | | | We hope these tips help if you are looking to choose |
| there is a trade off - a faster shutter speed will allow | | | | a new DV camera for sports analysis. Remember |
| less light onto the cameras sensor and therefore if we | | | | though, any camera can work; but if you want more |
| use a high shutter speed we need to make sure that | | | | detail you need to ensure that you recorded the detail |
| we have sufficient lighting as we discussed in the last | | | | with your camera. You cannot analyze details you do |
| blog. When looking at a camera for sports analysis, | | | | not have. |