Using After Effects for Scientific Measurements

[After Effects for science]

Hello all,

    I am looking to make some measurements (Feet per Second, angle and pitch) of movement of an object in video footage I have shot. Ultimately I was wondering if there is a way that I could use the tracking data to display the velocity of an object as it moves through the clip. The video is static and there are known distances in the clip, I was wondering if the motion tracker could be used to display, in text, on the footage, in Feet per second. I am also looking to find measurements of the angle and pitch of the object. If anyone knows how I could do this, I would be very appreciative. Thanks

[Dave_LaRonde]

I'm sorry, but you'll have to search elsewhere.  Adobe products simply can't generate the kind of precision it seems like you need.  You'd want to use purpose-built software for these tasks.

[Rick Gerard]

I will have to disagree with Dave on this one. The problem with any kind of photographic analysis is the accuracy of the photography. I have done a bunch of expert witness work analyzing photographs and videos and you can get pixel level accuracy with your measurements. The problem is not measuring the movement and position of the pixels, it is in the accuracy of the work you have done on location. If you are shooting you have to take precise measurements on location. If you are analyzing footage that is already shot you need to find something in the shot that has a known dimension. The analysis is not automatic. It requires extensive math skills and if you want to display that info in AE expression skills. I have done jobs that covered several acres with the precision down to + or - .5 inches. I have done close up photographic analysis with accuracy that I can certify down to 1/1000 of an inch, and I have done speed calculations accurate down to + or - 1/1000 mm per second. That kind of accuracy isn't fast or cheap.

That said if you shoot it right, take precise measurements when you set up the camera, correct for lens distortion, and have enough information to track you can accurately measure angle changes, speed, acceleration and about anything else that is happening in the shot. The accuracy depends entirely on your shot, your measurements, and your math skills. There is nothing about the process that is automatic.

If you have a sample of your footage I can at least point you in the right direction. If your footage is unusable I would be happy to offer some suggestions. I will agree with Dave on one point. There is software out there that is better suited to this kind of analysis but it is also not cheap and requires the same kind of precision required to do the job in Photoshop or After Effects.

[Mylenium]

Most of what you want could be calculated using expressions, but as Rick pointed out, it depends a lot on preparing the shots properly in the first place.

Mylenium

[After Effects for science]

Thank you,

   Yes the footage was shot with measurements in mind. I unfortunately cannot share any of the videos since they are considered not for public release. We used a Blackmagic Ursa Mini with a canon TS lens to correct for distortion. The camera was perfectly leveled and exactly perpendicular to the subject. Think of it as a giant potato gun that fires a bus sized projectile into the air, where we are capturing the object from beginning to end while maintaining the entire arch of its path in the frame. The object has distance markings on it so we have a known distance. I think I will try to convert the footage to a format that can be used in PCC so I can get my velocity. I was just hoping to give it more of a presentation appeal by using After Effects. Thank you all for your input.

[Rick Gerard]

A pencil sketch of the shot would help. Measuring the speed is just a matter of counting frames and AE has a built-in time function in expressions. Calculating the arc is just math. It will require some knowledge of expressions. The overlays are easy. AE can certainly help your presentation.

BTW, just putting on a nice lens will not remove distortion. Lightroom has lens profiles that work fairly well but I always do manual calibration for precise stuff. It amounts to shooting a grid and making adjustments.