Using my video camera as a speed gun

[jaypatel33]

Hi,

Am brand new to this forum. I have recorded my bowling action (the english game of cricket, where you throw/bowl the ball the the batsmen). It was recorded side on to my run up. I wanted to measure my speed, so I thought, using 2 consecutive frames from movie maker, giving a time of 0.04 sec. Then using Pixlr(free photoshop), overlap the two frames, and measure the pixel distance the ball has traveled. Then I use the diameter of the ball (known) to measure how much distance each pixel is in real life. Then I calculate speed.

This should be accurate, with the only uncertainty coming from the pixel measurements. The results so far have me questioning if there are other factors I have missed, I got most of readings at 40mph, this is very slow, spinners bowl at this speed, I have been told I am faster, then I have one reading at 75mph. The fast one showed really good technique, so is why is that fast, but the slower ones shouldn't be that slow.

Thanks so much for the help.

Jay

[lata]

Hi
and welcome to the forums

I assume you have used a camcorder to record video of your bowling.
If so then the post may be best in the Video Studio forum??

The camcorder will record video at a constant rate, for Pal 25fps, if HD you may get 50fps. NTSC 29 and 60fps
If the camera is far enough away to record the full pitch, stumps to stumps, you could count the number of frames it takes the ball to travel that distance.
Leaving the hand to hitting the stumps, assuming you do hit the stumps
The camera should be static, on a tripod.

[jaypatel33]

Hi
and welcome to the forums

I assume you have used a camcorder to record video of your bowling.
If so then the post may be best in the Video Studio forum??

The camcorder will record video at a constant rate, for Pal 25fps, if HD you may get 50fps. NTSC 29 and 60fps
If the camera is far enough away to record the full pitch, stumps to stumps, you could count the number of frames it takes the ball to travel that distance.
Leaving the hand to hitting the stumps, assuming you do hit the stumps
The camera should be static, on a tripod.

Hi, thanks for your reply. I'll move re post on the video studio, Just to quickly answer your question, I don't want to use the full wicket, as then I have to consider air resistance and bounce, and I wanted a reading out the hand so I can compare it with the pros, who readings are taken in the manner.

[BrianCee]

topic moved to VideoStudio

I think your on the right track - diameter of ball = known distance - so you can work out the distance travelled in 0.04 second - which suggests you are using PAL

don't think you could use hand to wicket any rate as you do not know exactly where your hand will be - also presumably the ball speed decreases (slightly) during it's travel

note that Trevor and I are both in the UK so understand the game of cricket.

at this moment though I can't think where you might be going wrong - maybe using frames further apart - say 10 frames = 0,4 second may give a more accurate result.

[jaypatel33]

topic moved to VideoStudio

I think your on the right track - diameter of ball = known distance - so you can work out the distance travelled in 0.04 second - which suggests you are using PAL

don't think you could use hand to wicket any rate as you do not know exactly where your hand will be - also presumably the ball speed decreases (slightly) during it's travel

note that Trevor and I are both in the UK so understand the game of cricket.

at this moment though I can't think where you might be going wrong - maybe using frames further apart - say 10 frames = 0,4 second may give a more accurate result.

Hi, thanks for the reply. It get difficult using more frames apart, because then you must move the camera further away, and harder to pick up on the detail. I have posted this on other forums, someone suggested because its progressive the ball might not be were it should due to compression. But apart from what he mentioned, not seeing where I'm going wrong. Thanks

[Ken Berry]

It would be helpful if you could tell us what make and model your camcorder is. Can you also right click on the video in the Video Studio timeline and copy ALL its Properties here, please.Then we might have a clearer idea of what we are dealing with in video frame terms.

[BrianCee]

I just did a quick sum - and according to my calculations a ball travelling at 60mph travels 3.5 feet in 0.04 second - and I am now wondering if using the ball as a reference distance compared to the flight of the ball is where you errors come in - a cricket ball is very small compared to 3.5 feet and even a very small error in measuring the diameter of the ball would result in quite a big speed error.

I wonder if you would get a more accurate result if you put a line of cricket stumps placed exactly 3 feet apart and then bowled along that line - making sure when you filmed at least some of the stumps were in shot.

That way you would get a more accurate measurement of distance which should allow you to make more accurate speed assessment.

[jaypatel33]

It would be helpful if you could tell us what make and model your camcorder is. Can you also right click on the video in the Video Studio timeline and copy ALL its Properties here, please.Then we might have a clearer idea of what we are dealing with in video frame terms.

Its a fairly inexpensive compact camera, Fujifilm FinePix Z90. I'm not sure what you mean by video studio timeline, I googled it, but come up with random results. Thanks

[jaypatel33]

I just did a quick sum - and according to my calculations a ball travelling at 60mph travels 3.5 feet in 0.04 second - and I am now wondering if using the ball as a reference distance compared to the flight of the ball is where you errors come in - a cricket ball is very small compared to 3.5 feet and even a very small error in measuring the diameter of the ball would result in quite a big speed error.

I wonder if you would get a more accurate result if you put a line of cricket stumps placed exactly 3 feet apart and then bowled along that line - making sure when you filmed at least some of the stumps were in shot.

That way you would get a more accurate measurement of distance which should allow you to make more accurate speed assessment.

You are right, I do seem to get consistent results with it. I also rechecked using the length of my arm as a different reference point, and got to similar numbers, usuallly out by around 3-4mph. I might use a cricket stump, like you said next time,

[lata]

Hi

Download the trial version of Video Studio X5, there is a link at the top of the posts.

Video Studio will allow you to insert the video file, view each frame, You can also create an Image Sequence, this will create a still image of each frame allowing you to easily view.

I guess the ball will take approx one second to travel the 22yds, that's approximatively one frame per yard. Obviously the ball will not be at a constant velocity, accelerating, so the point at which you take your image measurements is critical, if you vary this position then the results will vary as the ball is not travelling at a constant rate.
I do not know at hat point the ball gets to its max velocity, i guess that’s how good you are as a bowler.

Going back a few years now, I was pretty good, at least the batsmen always looked forward to my bowling.