Tracking Markers for TV Corner Pin

[Steve Roberts]

In general, tracking software prefers tracking corners. If you can zoom into the corner of a square or triangle, the tracking software should be able to follow it nicely. The problem with circles is when they are too big, the software can start drifting around the circle’s edge, since there’s no corner to grab.

… in my experience, at any rate.
Steve

[Aharon Rabinowitz]

I’ve been given stuff with dots and cross hairs, and both worked. I can’t say which is better. As long as your tracking points are really defined from anything else in the immediate area Both color and brightness), you shouldn’t have too much trouble – though ineveitably you will probably have to make minor corrections to your track – it’s almost never a free ride. But, using trackpoints will make life a lot easier – a lot of times I wish I had something…

I will say that feeding anything to a monitor may cause problems – at least with a tradiditional monitor. If you’ve ever watched the news when they showed a monitor in the BG of an interview, you can see the monitor refreshing itself – it blinks, and a line passes over it repeatedly. While the human eye can’t see this, it becomes very obvious on video. It may get in the way of tracking.

I don’t know if this is an issue on a flatpanel – I’d do some testing or ask someone who’s done this beofore about any potential pitfalls, just to be sure. I’ve never been given anything like that.

—————————————-
Aharon Rabinowitz
aharon(AT)yahoo(DOT)com
http://www.allbetsareoff.com
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[Mike]

Thanks so much for all the feedback. I’ll let you know how it goes!

[Alpay Kasal]

I’m a little confused about what you’re up to exactly, sounds like you’re putting green on the display, this would have helped me greatly in the past so I thought I’d offer this from experience…

I worked on a short film where there was camera motion and I corner pinned a bit of dv video onto the screen of an old television. I had to mask out the corners to match the curved shaped of the televisions bezel. as I look around my house, all my tv’s have a curved plastic bezel. I did not think of this initially and thought the effect would be super simple. the corner pinning worked fine but the curved masks were distorting a little with the handheld camera motion, I had to go in and fix stuff by hand. Just thought I’d share.

btw, i could not have used green or blue on the tv as it would have lit up the scene. i hope you can get away with that.

Alpay Kasal
Artist/Engineer
https://www.NYCRenderfarm.com

[Andrew Shanks]

No easy answer to this one. I did a show a couple of years back where we tried the old blue signal thing (the TV was fairly modern so would display blue if no signal was present). The biggest problem we had was that the blue spill you get from the screen is crazy bad, you end up getting very fuzzy soft edges around the screen and having to do a bit of spill suppression for the surrounding areas. Another option is actually sticking green or blue card (with tracking blips) to the front on the screen (hard to get card flat and non-creased, but still doable). the other option is to pre-edit whatever needs to be running in the screen, burn it to a DVD (in either looped form, or single play) and plug a DVD player in to cue the playback (make sure you have some sort of countdown leader on it so the actors have a warning about their cue).
As for tracking points, little squares of gaffer tape work well, make sure the colour contrasts with the screen colour you use. After Effects can have problems with tracking crosses if they rotate too far (since the program has problems dealing with the fact the original geometry that was looking like a plus symbol might now be looking like an X, you can of course sort that out by starting the track again when it goes astray (and it will take a new snapshot of the trget geometry from the position it starts tracking from). A tip with tracking things in AE is to create a new null layer and apply any transforms to that, ..then parent whatever layer (or layers) you want to move to that null. This way you can scale, rotate and move your layer independantly and it will always retain the tracked transform (as its following the un-changed null movement/transform).

Goodluck!

Andrew

🙂