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I have a few markers that I use to make augmented reality pictures for DIY projects. It's working fine when the camera is fixed. Now I would like to use them on a moving object to do basic motion tracking.

Here are some frame grabs. I moved the marker with increasing speed in front of my camera. By camera, I mean the built-in camera in my Samsung Galaxy S.

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Obviously this is not usable for motion tracking. I am a programmer and I'm interested in computer vision, but I am not a videographer, so feel free to put as much details as you want in your answer. I am not familiar with the characteristics of video capture hardware.

My goal is not to buy a high speed camera to duplicate what they do in Mythbusters for example. For example, I would like to be able to track juggling props, if you need an idea of the speed of the targeted objects.

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2 Answers 2

As far as I can tell, what you are asking for is a camera that can capture your content into smooth, sharp and crisp video that will remain sharp and unblurred.

Most cameras can do this. It's not so much about what camera you get, but rather about what settings you use and what conditions you film in. To explain further, you need to film with a short shutter speed and in a well-lit environment. The faster your object is moving, the shorter shutter speed and the more light is needed to keep it sharp and neat-looking. You will also want to make sure that the aperture of the camera lens is completely open (to let in as much light as possible). There are more factors to consider but these are the most important.

Now, obviously the camera on your phone is not optimal to do this since you can not change any of the settings I mentioned above. What you need to look for is a camera that let's you change the aperture and shutter speed settings. That is the most important and should be sufficient for your needs. Most DSLR's (with a video function) and camcorders today allow this - at least to some extent.

Also, after taking a second glance at your pictures, I just realized that you might have used some kind of digital zoom for this. Don't, it will be way harder to get any type of quality content from your camera in that case. Also, try to shoot in as high of a resolution as possible. At least 720 (HD).

I hope you understand this and that it helps you some. English is not my first language so the post might be a bit messy. But hopefully someone can edit and clean it up a bit. With that said, best of luck to you! I hope you find what is right for you.

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I can see what you are talking about for the digital zoom problem. I didn't used the zoom, so I guess the staircase effect seen on the first image, near the highlight of the top quadrant of the marker is due to some internal upscaling. Anyway, I never intended to use my smartphone as a serious camera. –  Antoine Lecaille Dec 10 '12 at 16:13
    
Ok, well what is your price range? Or what other cameras do you have available to you? –  burnso Dec 10 '12 at 16:23
    
In addition to this, see if you can get a camera that can shoot a high number of frames per second (50, 120, or even more). More frames gives your motion tracker more data to work with. –  Bart Arondson Dec 10 '12 at 22:17
    
Not sure if that would matter much in this case. He still needs to track every single frame (even if it's done automatically), so I don't quite understand how much help a high speed camera would be? –  burnso Dec 11 '12 at 1:27

When tracking there are two (main things) that you need to be concerned with in tracking. While there are many variables that need to be taken into account, when shooting there are two things that you should keep in mind.

First off, contrast, 99% of all tracking software uses contrast in the luminance channel (brightness) to determine a point and where it is going, green and black is not going to work very well. White and black is your best bet...

enter image description here

Second is going to be the camera you are capturing the video with, obviously then this introduces a lot more variables...you want the footage to be properly exposed, and the shutter to be correct, the lower or too high of a shutter will make it more difficult to track shots.

Also when choosing a camera understand compression, the more compressed an image is the harder it will, also the lower the resolution. For example, 1920 TV has a better resolution than a 720 TV. But compression also matters, an image could be as big as texas but if it is highly compressed chances of pulling a track out of it is unlikely...

Take a look at this image, you can see all the images are the same "resolution" however the further right the more compressed the image is, and the harder it is to detect edges...

enter image description here

So now that you understand how to capture your footage, you need to check out a simple tutorial or two on how to track your footage. there are several types of tracking but from what is sounds like you are looking to track a point or track a motion of a point. Your best bet is going to be After Effects motion tracker.

You can get a 30-day free trial from the adobe website, and check out some awesome tutorials on VideoCopilot.net on how to do tracking.

I hope this helps

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