Using Video Overlay to Compare Two Athletes' Shuttle Runs

A shuttle run is often used in professional sports combines to determine the fitness of a prospective athlete. A shuttle run consists of an athlete running back and forth between two lines approximately 30 feet apart, touching each line before heading back the other direction. The videos below were taken at a basketball court that already has a series of lines marked out. We used those lines to mark the beginning and end points of the run, rather than measuring out 30 feet.

This exercise is a way to evaluate an athlete's speed, quickness, and agility. According to the National Academy of Sports Medicine, “speed” is defined as the ability to move the body in one intended direction as fast as possible, “quickness” is the ability to react and change body position with maximum rate of force production, in all planes or directions of motion, from all body positions, during functional activities, and “agility” is the ability to accelerate, decelerate, stabilize, and change direction quickly, while maintaining proper posture.

Most testing sites simply use the athlete’s overall time as a way to make this evaluation, as shown in the first two parts of the video below (the first subject recorded a time of 10.377 seconds, and the second subject recorded a time of 10.010 seconds). But knowing the overall times only tells us which subject completed the trial the fastest, not why or how one was faster. In this week’s article, I’d like to discuss the value of using the video overlay feature to determine the point or points in the run where one subject gains an advantage over the other.



Video overlay can be used for a wide variety of comparisons. For example, it can be used to compare:
• A single athlete, before and after training (as a way to determine the effectiveness of training)
• A single athlete, before and after rehab.
• Multiple athletes

Video overlay and athlete comparison works best when the subjects are moving from left to right, or right to left,(sagittal plane) across the camera’s view, as it’s much easier to view when the separation between the athletes occurs during the trials. During the 2009 NFL combine, the television coverage tried to use this technology for the 40 yard dash, but they overlaid too many athletes’ trials (10 or more) on top of each other; and since there was very little difference in the athletes’ times, the end video looked like a bit of a mess. Therefore if you plan to use video overlay to compare athletes, don’t overlay more than two or three subjects at the same time.

To make things interesting for our recordings, we chose to make each shuttle run turn facing the camera, so there are two right turns and one left turn in each trial.

Take a look at the third part of the video (showing the overlaid athletes), to see where the separation between these two subjects occurs.

We see that the subject in the gray shirt (we’ll call him Subject 2) gets off to a slightly faster start than Subject 1 (blue shirt), and reaches the far cone first. After making this right turn, the distance between the subjects remains the same until they return to the starting cone, so we can assume they both came out of the first right turn in the same amount of time, and that they ran with the same speed between the far cone and the starting cone. Coming out of the left turn, Subject 2 starts to break away a little more, so it’s possible he is faster pivoting off his left leg. And after making the final right turn, the distance between the two subjects remains about the same after the left turn through the finish.

So what were the turning points in this race? It seems Subject 2 got off to a faster start, and was quicker coming out of the left turn; so it may be useful for Subject 1 to work on his start (see http://videosportsanalysis.blogspot.com/2009/08/video-analysis-of-sprinting-from-start.html for details on how to start fast)> We also see that Subject 1 lost some time in his second turn and acceleration from there. He may also work on strengthening his left leg, to help him make the left turn a bit faster. We also happen to know that Subject 1 has had rehab on his left knee in the past and therefore may have a weakness or instability that still needs work.

By using the overlaid video, we were able to get a lot more information about these trials than just who finished first, and can use this information to make specific recomendations to an athlete's training regimen or to assess the rehabilitation of an athletes injury.

As you can see video overlay can be a powerful tool when evaluating an athlete’s performance. We value your comments and would be happy to answer any questions.

Which Sport Has Bigger Hits, Rugby or Football?

Most of us who have watched or played both Rugby and Football know that the tackles are often hard and dangerous. We also regularly try to compare the hits. Is it worse to be hit hard in a rugby tackle or in football?

On the football field the force of the hits look more spectacular. Players can be tackled in numerous ways, even with the head. The aim of the tackle is to stop forward progression and bring the player down to stop the play. In a great tackle the player is also trying to make the receiver or ball handler fumble. In getting hit there is the added concern for the wide receivers who have to watch the ball and often jump for the catch. They can get hit while still in the air and without expecting it. Of course the athletes are also wearing padding and helmets and therefore have some form of protection.

In rugby the tackle is meant to stop forward progress of the ball handler and to simultaneously bring him to the ground so that he can not pass the rugby ball out quickly. Tackles in rugby often need to be lower (around the knees or waist) to ensure the player goes down. The tackle also does not stop play and players need to be ready to get up and tackle again almost immediately. Of course in rugby there are no helmets or pads, so there is little protections for a big hit.

OK so which tackle is harder on the player? We could measure the speed of the players as they run into each other and weight that against the benefits of the padding. In the end both sports have big hits and there are too many differences in the rules of the game and the equipment to truly compare them. So take a look at these two videos, the first of big hits in rugby and the second of some big hits in football and make up your own mind.





Hope you enjoyed watching those big hits. The Tri-Nations Rugby Tournament between South Africa, Australia and New Zealand is nearing an end as South Africa continue to dominate World Rugby. Meanwhile the NFL preseason is in full swing and starts proper in mid September. So enjoy the big hits from the upcoming Tri-Nations games and NFL season.

Let us know which sport you think has the bigger hits and why.

Analyzing Usain Bolt's 19.19 Second 200m World Record

The Scientific Research Project at the 2009 IAAF World Athletics Championships has released the data for the 200m final and now we can break down Usain Bolts incredible 200m World Record of 19.19 seconds.

Click on the table below to get a closer look.

Let's pick out the key points for this race and see if we can compare them to his 100m splits.

1. Bolt's reaction time in this race is 0.133 seconds. This is much better than his 0.145 second 100m world record reaction time. However we have already discussed this in a previous post and know that Bolt can start fast too.
2. As expected Bolt runs the second 100m (from 100-200m ) faster than the first 100m. This is expected, as the start and getting up to speed takes time, while the second 100 meters can be run at close to maximum speed. Bolt's first 100m was run in 9.92 secs with the second hundred taking only 9.27 secs (a negative split). Interestingly, Michael Johnson ran the second 100 meters of his then World Record breaking 19.32 sec 200m race in 9.20 secs, which is faster than Bolt's second 100m in this race.
3. Bolt's maximum velocity during the 200 meter race occurs somewhere between the 50 and 100 meter mark. His average velocity over this 50m part of the race is 11.57 m/s (25.88 mph). In comparison his 100m maximum velocity was 12.27 m/s (27.45 mph). Once again this is to be expected, as the 200m athletes needs to have reserves to complete the race and cannot run at the same speed as in the 100m race.
4. Bolt slows down over each of the last two 50 meter splits as he begins to fatigue, covering each of the following 50 meter splits 2 tenths of a second slower. Watching the race, we can see that he is really straining to run fast, but he is still slowing down. It is expected that any athlete will slow down over the last 100 meters as the muscles tire, two hundered meters is a long way to go at full speed. We have mentioned that in this World Championships Bolt had already run four 100m races and three 200m heats before lining up for the 200m final. This has us excited at the prospect of seeing Bolt break this 19.19 second World Record, when he is fresh and has not run seven previous races.

All that is left to say is that we can expect Bolt to go faster in the 200 meter and 100 meter races in optimal conditions.

There is one record he does not hold yet and that is of the fastest 100m relay split. This record is held by his Jamaican team mate Asafa Powell in 8.70 secs. The anchor leg relay split is much faster than any of the other sprint splits, because the athletes have a flying start and are therefore able to reach top speed much sooner in the 100 meter distance. If Bolt anchors the 4X100m relay in Berlin this week, we expect that relay split record to be broken.

Comparing Usain Bolt's 100 meter and 200 meter World Records

Usain Bolt continues to amaze us with every race he runs. In destroying his own 200 meter world record from the Olympics, he has now set 5 world records in five Olympic or World Championship event finals in a row.

Watch video of the 200 meter race from the 2009 IAAF World Athletics Championships below. The final recorded time and the new record stands at 19.19 seconds, an incredible 0.11 seconds faster than his previous world record.



The 200 meter sprint record is usually a faster time than if you had to double the 100 meter record. This can be seen if we compare the more recent (since the use of electronic timers) progression of world records between the 2 events. As an example, when Donovan Baily held the world 100m record of 9.84 in 1996, the 200m record was held by Michael Johnson at 19.32 secs. This 200m time is faster than double the 100m record at the time.

In both the 100 and 200 meter races, the athletes start from the blocks and it usually takes them around 60 meters or more to reach maximum speed. In fact we saw from analysis of Usain Bolts 100m world record that he reached top speed at 65 meters in that race. Now in the 100m, the athletes maintain that speed for 40 or so more meters, while in the 200m they have 140m more to go and therefore maintain their top speed for longer. In fact the 200m race often has negative splits for the top athletes, meaning that they run the second 100 meters faster than the first 100 meters.

It is therefore interesting to note that if we double Usain Bolts 100m time (9.58) we get 19.16 secs, which in this case is faster than his new 200m world record of 19.19 secs. I am not trying to make the case that this 200 meter world record is not extraordinary, but why is this the case?
Watching the 200m race, he seems to be straining at the end, by this stage of the race his muscles must be burning, as he tries to maintain his maximum speed. He also said in an interview after the race that he felt tired and well he should after running all the 100m and 200m heats and finals. It is possible that this fatigue meant he could not run the 200m as fast as he possibly can. Seldom has the 100m and 200m world records been held by the same athlete or even broken by the same athlete at the same event and so this may be a factor in his 200m time.

Examining the splits and his maximum velocity to compare his 200m to his 100m world records, will give us more insight into what we can expect from Bolt in the future. From this past records history we can speculate that his 200m record is going to be smashed again soon and the 19.0 second barrier is not out of the question.

It is fantastic watching such an incredible athlete run and we hope to learn as much as possible about his biomechanics by watching and analyzing the video footage.

Can Usain Bolt Run Any Faster?

In a recent post we asked the question: How fast can Usain Bolt Run? In this post we introduced you to a study that suggested he could have run the 100 meters at the 2008 Beijing Olympics in less than 9.6 seconds.

At the 2009 IAAF World Athletics Championships, today he proved just that, shattering his own World Record by running the race in 9.58 seconds. Even then he still had time to take a look out of the corner of his eye at Tyson Gay, his closest competitor, who ran an impressive 9.71 seconds

If you missed this amazing race, take a look at the video below.



Unbelievable! The only question left is how much faster can he go? Bolt himself believes that he can run the 100 in 9.4 seconds. To us this seems a bit out of reach, although we believe he will go faster than 9.58.

We would love to hear what you think.

Video Analysis of Sprinting: From the Start

In the 100m and 200m track sprinting events, the start can win or lose a race. In the 100m the winning difference is often measured in 100ths of a second, therefore any advantage that can be gained at the start could be crucial.

At the IAAF World Championships next week, Tyson Gay will take on Usain Bolt for the title of worlds fastest man. So far in 2009 both athletes have put up some impressive times and the first meeting between them this year should be fast, close and exciting. Usain Bolt is the Olympic champion and world record holder. We have previously discussed how fast he could possibly run. Tyson Gay is the reigning World Champion and recently ran the 100m in 9.75 seconds at the US Championships.

With both athletes being at the top of their game, victory may be decided by their start. Neither of them is known for their explosive or fast starts. Bolt has an incredibly long stride length and eats up ground with each step while Gay has unmatched leg speed. The start though is crucial and we have therefore decided to look at some video and examine the start.

Below is some front on video of Tyson Gay at the US Championships. We want to focus on his start.


A good start requires that the athlete sets up correctly. Here are some key factors for the set position before the start gun sounds.

1. The hands are set up on the line and the shoulders and upper body should lean forward over the hands. Track coaches suggest an angle of about 15 degrees (The angle between the shoulders and hands and the vertical). Although we cannot see the angle at which Gay is leaning (this would need a side on view of his start), we can see that he is leaning forward and ready to explode from the blocks.
2. The angle of the knees in the start position must allow the athlete to push away from the blocks with as much power as possible while at the same time being able to get their feet through to begin running. The optimal bend of the front knee should be around 90 degrees to provide the biggest lever to produce push off. The back leg needs to be bent less than this at about 60 degree so that it is able to still push off hard but will straighten before the front leg and have time to come through for the first step.
3. Both legs need to push off almost simultaneously at the start of the race. The athlete cannot be sitting back on either his front or back leg at the start.

Tyson Gay sets up well and in this video he explodes from the blocks, pushing off with both legs quickly. Both legs straighten completely, with the rear leg leaving the blocks and starting to drive through before his front leg (left leg) is completely straight.

Gay also uses his arms to explode out of the blocks, as well as maintain good balance. Watch as his right arm drives backward and his left forward. This motion provides extra forward momentum, but it also ensures that as he starts he does not fall over to one side. The arms act as a counter balance to the motion of the legs. In this start his right leg will take the first step on the track and therefore his left arm needs to be forward to balance this motion.

Moving forward to that first right foot step on the track, we can see that Gay's head and chest are still down low. His arms are driving hard and fast. If you pause the video you will see them as a blur. We can also see that his first step is not too long. In fact his head, chest and hips all remain in front of his foot for this first step. This allows him to continue to stay low with his body. If he took a longer first step, it would force his chest up, which would in turn slow down his speed. His chest and head stay down for as many as 16 steps allowing him to lean forward during this start and continue to accelerate.

His start technique looks great here and although we do not know what his reaction time to the gun was, we can see that he was able to accelerate well from the start and this is why he put up such a fast time.

As I looked through more videos on Tyson Gay's start, I came across one from tttjump that suggested that Gay's knee rolls forward at the start. If you study the slow motion of the start in the video above you will see what this means. Gay's front leg (his left) moves forward and down, in fact bends a little more, just after the start and as his hands leave the ground.

The suggestion is that this extra bend of the front knee at the gun, causes a delay in his ability to get off the blocks. On closer examination we can see that his back foot is driving already (straightening) as his front knee "rolls" forward. This may be causing him to push off with less power from his back leg as he may need to slow it down, to give the right leg time to get into a position to start its push off.

From a biomechanical standpoint, this would suggest that Gay's front leg is not bent to the most optimal position to explode out of the blocks. He may be bending it a little more after the start to get more push off power. The split second it takes to bend the knee that little bit more and the small amount of back foot push off power that he may lose, could determine the outcome of the race against a phenom like Usain Bolt.

Once again from the standpoint of biomechanics, this problem could possibly be solved by simply adjusting Tyson Gays starting blocks or position slightly, allowing his front knee to set up in a more optimal position for his starting style.

Of course for this World Championships, it is too late to make any changes and Tyson Gay should provide Usain Bolt some really stiff competition when they hopefully meet in the final in Berlin.

If you will be watching or filming some video of any of the action at the IAAF world championships and would like to share some video for analysis, please let us know.

How Fast can Usain Bolt Run?

The IAAF World Championships begins in less than a month and all eyes will be on the 100m and 200m world record holder, Usain Bolt from Jamaica. We all remember the Beijing Olympics in 2008, when Bolt ran the 100m in 9.69 seconds, throwing out his arms and pumping his chest before crossing the line. There has been a lot of speculation about how fast he could have run with some suggesting a time of 9.55 seconds http://sports.espn.go.com/oly/trackandfield/news/story?id=3583692 .

The publishers of the study above, made use of video analysis to estimate this potential world record time. In fact they used video from Beijing Olympics broadcast productions from NBC, BBC and NRK (a Norwegian Channel). If you are a regular reader of our posts you will already know about many of the techniques they used to analyze the video. Lets look at how they did it.

When you or I setup to capture video of a sporting performance, we know how important the position of the camera is. In this case however the researchers did not have access to the stadium and athletes in Beijing and therefore had to make use of broadcast footage. In most cases this footage includes moving cameras and camera angles that are not always conducive to accurate measurement.

The publishers of the article used basic physics to estimate the possible finish time for Usain Bolt had he not celebrated 20 meters before crossing the line. The basic equations are well known:
Velocity (speed) = Distance/Time
Acceleration = Velocity/Time

So if we can find the distance Bolt covered and the time he took to cover that distance we would have his velocity or speed. We could measure that speed, from the video footage, over numerous intervals to determine how it is changing. Likewise, if we know his velocity (speed) we can measure his acceleration and how it changes over the same intervals.
The publishers of the study estimated Bolts speed and acceleration at the interval before he started to celebrate. At this point his speed and acceleration slow. To determine the predicted finishing time, the researchers assumed that Bolts acceleration could be maintained over the last 20 meters of the race, had he not celebrated. In this way they were able to predict a finishing time of 9.55 seconds.

You probably want to know how they were able to determine distance covered and the time it took. This information was all obtained from the broadcast video. The video used was from NBC and can be found at http://www.nbcolympics.com/video/share.html?videoid=0824_HD_ATB_AU_CE552 . Below is similar video of the race :


In the video you will see the camera rail running from the left to the right at the bottom of the image. This camera rail has bolts spaced evenly along it. By knowing the distance between the bolts on the track and that the start line is at 0 meters and the finish line at 100 meters, we can determine Usain Bolts position relative to the rail bolts at numerous intervals.

You will also see the stadium time clock and the broadcast time clock in the video. These clocks can be used to determine the time at which Bolt reached each interval.
We now have all the information we need. Distance covered and the time it took. From this we can determine his speed and acceleration at all intervals and predict his finishing time had he not begun his celebrations early.

We would like to thank the study authors H. K. Eriksen, J. R. Kristiansen, Ø. Langangen and I. K. Wehus for doing this fun study and we look forward to seeing whether Usain Bolt can get anywhere close to this predicted World record at the IAAF World Championships in Berlin in August.

Please let us know if you want more details on this study or just want to leave a comment. We love to hear from you.

Andy Murray's Tennis Serve

Last week, Rafael Nadal won the 2009 BNP Paribas Tennis Tournament at Indian Wells, California, defeating Andy Murray easily in the final.

As we watched the tournament, we heard frequent discussions of Murray's second serve, and that if he could develop a better second serve he would be almost unstoppable. Of course, he was almost unstoppable at Indian Wells, but did lose badly in the final, mostly because of poor serving. In that final match against Nadal, he lost his service games four times and won only 6 of 16 (38%) of his 2nd serve points. Let's take nothing away from Nadal though; he has the best return game in tennis, possibly the best ever.

All tennis players, including beginners, know the importance of the serve. A good serve can result in easy points and puts pressure on an opponent. The first and second serves in tennis usually have different goals. With your first serve, you want to win the point with an ace, service winner, or at least put your opponent in a defensive position for the next shot. The first serve is generally flat and fast, and you can take more risk, knowing you have an attempt at a 2nd serve if you need it. The second serve is your backup safety. Your priority is to get the second serve in and start the point. If you miss the second serve, you will double fault and give your opponent a free point. Most tennis players put a lot more spin on the second serve, but this tends to reduce the speed of the serve.

Because of the slower pace, the second serve often gives the receiver plenty of time to get into position to hit an aggressive return. However, if you can make your second serve look similar to your first serve, at least in terms of the service motion, you can make it difficult for the receiver to predict the speed (and type of spin) of the serve, and you may retain a significant advantage, even as you serve slower and with more control.


We found some video of Andy Murray's first serve and decided to look at it from a biomechanics point of view. This video is set up very well for video analysis. The camera is set up along the baseline, which allows us to get a side-on view of Andy during his serve. We can also see the complete service motion in the video, including the racquet head, and can see the racquet make contact with the ball. It would have been great if we could've seen the complete ball toss (the ball goes out of the top of the screen) and if the camera had been stable and mounted on a tripod; but in general, this is good video sports analysis footage.



The power in the tennis serve, like many throwing or hitting sports (baseball hitting and pitching, football throw, and golf) is created by a chain of events. Each part of the body loads up with energy and transfers its energy to the next link in the chain. The timing of this energy transfer is critical to creating racquet head speed and therefore a good, fast serve.

In Andy's serve, we see how he starts with his knee bend as he throws the ball up. You may also notice that as he bends his knees his hips turn away from the court. He then transfers this energy now stored in his hips by bringing his back foot up to his front foot and rotating his hips into the court. Once again notice that as he rotates his hips back into the court, his shoulders now rotate away. This counter rotation in both hips and then shoulders creates the potential for racket head speed; Andy is coiled up and ready to explode his racket toward the ball.

As he does this, he releases the potential energy, rotates his shoulders back into the court, and throws his racket at the ball. All these energy transfers add up to create the speed with which he will hit his serve. If his timing is off, his speed will not be as high.

The ball toss is, of course, just as important. If you do not throw the ball consistently, it will be very diffcult to perfect the timing of your kinetic chain (described above). Andy's ball toss is high and a falls about a foot inside the court. If you want to hit a good hard serve, the ball needs to be in front of you, so that your body and racquet are moving forward when the ball is struck. If the ball toss is directly above your head, it is much more difficult to get theball moving forward with as much pace.

Ok, so Andy has a great first serve, and we can see that here. It is his second serve that the commentators were discussing. Unfortunately, we were unable to find any good footage of his second serve to compare it to his first serve. We are sure his coach is working hard on improving his kinetic chain sequence and timing to make it more difficult for his opponents to read his second serve.

Please post comments and let us know what you think, or whether you have any questions or suggestions. We would be delighted to hear from you.

Sports Analysis: The Camera Specs

In the last blog Video Analysis of Sports 101 we said that we would discuss what makes a good camera for video sports analysis, so here it is.

If you already have a digital video camera there is no need to go out a buy a new one simply based on our recommendations here. If you follow the setup rules we discussed in Video Analysis of Sports 101 you will be able to obtain great footage that you can analyze.
However, if it's time for you to pick up a new DV camera, then getting the right camera can really help you obtain excellent sports analysis footage and make your video analysis clearer.

Speed and Size
Like most sports, a good sports analysis camera needs speed and size. There are a few different speed and size measures of a camera and they are discussed below.

Frame Speed
Most off the shelf DV cameras have a standard frame speed of 30 frames per second or fps(NTSC) in the North America and 25 fps (PAL) in most of the rest of world. What this means is that the camera records 30 pictures every second, one picture every 0.03333 seconds. 30 frames per second is the speed at which most regular television is recorded and viewed. When these 30 frames are played back at full speed every second, our brain is unable to distinguish between the individual pictures and we see a flowing video.
However, if we want to analyze a tennis serve then we need to slow down our video and look at each one of these 30 frames of every second and this is where a problem may arise. As the serve is generally a quick motion, we will probably find that if we only record 30 fps then the arm will look like a blur during the serve motion and we will be unable to analyze it properly. To solve this problem we can record the motion at a higher frame rate, say 60 fps and get double the amount of pictures every second. This will give us more data to analyze and reduce the possibility that the motion will be blurred.
In general the more frames we can capture per second the better our analysis can be. Luckily though there is a limit. In most sports when analyzing the human body movement 250 fps is sufficient. If we then want to include say the golf club or tennis racket and analyze its movement, we once again need higher speeds maybe up to 500 fps.

Many sports TV programs now use high speed cameras to analyze sports. Here is some recorded high fps video. A lower fps camera would often show blurring as we watched each frame like this.


Unfortunately though there are very few off the shelf commercial cameras that can record high frame rates. You can find some cameras that can record 60 fps, but if you want to go higher, costs can increase substantially. We think a 60fps camera is a perfect start for doing your own analysis.

Shutter Speed
We can get away with the usual 30 fps as long as we have a high shutter speed. Shutter speed determines exposure time, or how long the cameras sensor is open to receive light and therefore record the frame. In sports analysis the higher the shutter speed the less blurred our image will be. However there is a trade off - a faster shutter speed will allow less light onto the cameras sensor and therefore if we use a high shutter speed we need to make sure that we have sufficient lighting as we discussed in the last blog. When looking at a camera for sports analysis, look at the shutter speed and whether it is manually adjustable. A camera that automatically adjusts its shutter speed to the lighting conditions can make you forget the importance of ensuring good lighting on your subject.

Resolution
We all know about resolution from high def televisions. High def television can only display those high definition images if they were recorded by a high definition video camera. The resolution of a video camera is a measure of how many pixels our camera sensor has. Luckily for us most video camera manufacturers are now making HD cameras with about 1920x1080 pixels or 2.3 Mega pixels. Of course a higher resolution is always better just like it is on our TVs.



Lens Choice
There are 2 important aspects of a lens for sports performance capture, aperture (f-stop) and focal length and optical zoom.

Aperture

The aperture or f-stop is a measure of the amount of light the lens of the camera will allow through. A lower number will allow more light into the camera and a higher number less light. Most DV cameras have f-stops as low as 2.5 which is good enough for sports analysis purposes. Once again just like with shutter speed there is a trade off. A lower f-stop can often result in a lower resolution image. This does not mean that the cameras sensor has less resolution but that there is a trade off with lighting and quality. Once again this points to making sure you have a good light source for your recordings. With a good light source you can use a lower f-stop and therefore obtain a better resolution image.

Focal Length
The focal length is the distance from the lens to the camera's sensor. A smaller focal length means that the camera will capture a wider angle of view and see more in the frame, while a large focal length allows the camera to see more details further away. Focal length and optical zoom therefore are linked. Optical zoom of course allows us to zoom in or away from an athlete.

Most DV cameras come equipped with optical zoom and will read something like 49-735mm, which is the range of focal lengths that can be achieved with this camera.

The more optical zoom we have the further away we can be while still recording excellent footage for analysis. Now its up to us to use that optical zoom effectively by positioning our athlete correctly in the field of view. Check out Video Analysis of Sports 101 for details.

Also don't get tricked by digital zoom. Digital zoom is not our friend and if used can reduce our actual sensor resolution considerably. It is far better to reposition our camera closer to the athlete than make use of digital zoom.


We hope these tips help if you are looking to choose a new DV camera for sports analysis. Remember though, any camera can work; but if you want more detail you need to ensure that you recorded the detail with your camera. You cannot analyze details you do not have.

We welcome any comments or suggestions on our blog. Have a great week.

Dudley Tabakin