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August 12, 2008 at 6:10 PM #43808
I’m doing a school-related science experiment involving how steady a camera is under certain conditons. I need to find a way to measure how steady the camera is though. Is there any kind of software that you put the video into or a something i can attach to the camera. During the experiment the camera will be attached to a a tripod and in a controlled enviorment. I have talked tosomeone in the filming field andshe said that there is a way, but she couldn’t remember how. Does anyone have any suggestons?
August 12, 2008 at 6:31 PM #183613AspyriderParticipant
You would probably need a instrument that measures vibration. Check with your science teacher, the school may have a device.
August 12, 2008 at 6:41 PM #183614
Hrm… youcould put accelerometers on two sides (likeleft side andbottomofthecamera)to getanidea of how much it acceleratesin up/down andleft/right directions (youcan put one onthe backtoofor forward/back).Then using that and some calculus youcouldfind out how much it actually moved.
Anothermethod, that probablywouldn’t be as accurate,would betofilm a special “scale” whichis a seriesof verticaland horizontal lines.Then you “measure” (count) how many lines you “move”inthe videofootage.Depending on yourcamera’sresolution and how fine youcanmakethelines, youcan get decently accurate,but probably notas accurateas the accelerometers. Since you’ll be using the camera’s footage in this suggestion, you may want to do both with the stabilization off and on to see the effectiveness of the optical or digital stabilization.
Athird way, that I’m not sure how wellitwouldwork,isto attach some lightweight rods (wooden dowelswould probably work well) onthecamera in thesame kindsof places asthe accelerometersImentionedearlier.Then using scales (rulers might evenwork wellenough for these scales)measure how muchthe dowels move along the scales (the scaleswould be measuringthe furthestpoint away fromthecamera onthe dowels).
Thoseare myinitial thoughts…there’sprobablya muchsimpler way…
August 12, 2008 at 7:06 PM #183615
Thank you. Could you please explain accelerometers a bit more? I like the sound of it. I’m to young to understand calculas but i might be able to find someone who does.
August 12, 2008 at 8:11 PM #183616
Acceleration is the rate at which an object speeds up or slows down (more accurately, acceleration is the rate of change in instantaneous speed of an object over time… but I don’t think we need to get quite so technical :-P). An accelerometer simply measures the acceleration. Depending on the accelerometer, it can measure it in one direction or multiple directions.
These devicescan getfairly expensive, and sometimes youneed special connectionsto acomputertorecordthedata.Therearemany programs thatcan calculatethe distance traveled and/orthe velocity ofthe device (it’s simplecalculus, butiftheprogram candoit for youto the amountof sigfigs you desire,why not?).You might wantto check with your scienceteachertoseeiftheyhaveany.
August 12, 2008 at 8:18 PM #183617D0nParticipant
I’m confused….you said:
“During the experiment the camera will be attached to a a tripod and in a controlled enviorment.”
On a tripod your camera should be rock solid, and have no measureable shake.
so you’d wind up testing how stable you tripod is?
or perhaps how stable the ground (platform, floor etc) is?
or are you testing to find out if your cameras image stabilizer will induce shake on a stable camera?
August 12, 2008 at 11:19 PM #183618D0nParticipant
for what it’s worth….
If I wanted to find out how stable the floor/ground was I’d put my video camera on a tripod.
I’d set up a target with a grid (ie grid paper with a bullseye drawn on it) and center it in the viewfinder.
I’d use my cameras still image capture to snap a photo. (using remote).
I’d run the video for about an hour. (using remote).
I’d open the still in photoshop and cut it in half diagnally and leave half transparent.
I’d open the file in my nle and overlay it on the video.
I’d speed the video up.
on play back, any jitter in the video should be noticable, and measureable.
August 13, 2008 at 12:01 AM #183619
That’sa much better expansion on myidea number 2!The only thing I would add to that is, if you are putting the camera on a tripod, you might want to set it up so you can zoom all the way in. That will make even little jitters more noticable. Of course, if the jitters are too big that way, just zoom out a bit.
August 13, 2008 at 4:14 AM #183620CoreeceParticipant
I would highly recommend using the motion tracking feature within After Effects.
If you don’t have it, you can download the 30 trial at http://www.adobe.com/downloads/
-Once you have imported your footage and dragged it into a new composition, go to Window>Workspace>Motion Tracking. These buttons are located in the basic tool bar drop down menu.
-The motion tracking panel will open. Click the “Track Motion” button.
-A small box with crosshairs in center will appear over your video called “tracking point 1”.
-Drag the box over a small stationary object in your video that has a high contrast to it’s surronding colors. Make sure the crosshairs are right at the edge of the border of thetwo contrasting colors.
-Make sure the cursor in the timline is at the begining of the video and click the analyze forward play button in the motion tracking panel.
-When the video is finished playing, twirl down the video’s properties in the timeline. Youwill see an itemcalled “tracker 1;” twirl down it’s properties. You will see another item called “tracking point 1.” This is where all the tracking data is recorded.
-The data isstored in keyframes that are recorded in real time at the rate of 30 keyframes per second. Each keyframe contains the X&Y coordinates for the positon of the stationary point you chose in realation to the movement of the camera at that specific frame. It also gives you keyframed information on the accuracy or “confidence” of its tracking. If you choose a good high contrasted point, there should be no problem obtaining 97-99% accuracy or reliablity.
-The keyfames are located in the items named “feature center” “confidence” and “attach point”
-You can than compare the X&Y positon coordinates in the “feature center” to determine the steadyness of the camera.
-There are 1800 data sample reorded every minute, allowing you you determine the direction of the movement and the point in time that movement occured down to a 30th of a second.
-If you don’t have the ability to analyze every frame, it should be acceptable to compare only the position coordinates given at each second.
-The tracking data is also visually graphed over your video for an additional reference.
August 13, 2008 at 5:09 AM #183621
Thank you, those are very good suggestions. D0n, i think i’m going to test out yours. Thank you so much, I am testing how steady the camera is under conditions (in this case altitude) which will cause swaying of the ground below the camera. Thank you so much.
August 15, 2008 at 4:56 AM #183622AnonymousInactive
I just thought I’d add support for the graph paper idea with a little twist. Attach a laser pointer on the camcorder and aim it at the center of the graph paper. You will have easily quantifiable results if you draw a spot on the graph paper that is where the laser rests at the start. Now in any frame, if you measure the direction and distance between the spot & the laser point then you will know how far the camera has moved from the start or the magnitude of the movement. By comparing the distance between the frames, you can calculate the acceleration. It is easiest to use polar coordinates for measuring, but XY coordinates make calculating accelerations easier. If you have trouble with the math, I can show you how it works. Just remember, when you watch the video, the laser will appear steady and the graph paper will appear to be moving. Measurements are made from the laser spot to the center target, using that value and knowing the distance between the camcorder & the graph paper, we can calculate the angle of the camcorder’s deflection at any given point. Sorry I’m getting carried away. I really love math, especially when there is an actual purpose to the numbers.
Have fun with your research.
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