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[podmonger]

I'm going to be testing a wide tracking shot of two dancers, and we're expecting to paste white squares on the wall and hang some ping-pong balls from the grid. However, I'm not sure of the optimum density of ping-pong balls.

If it's an issue of having a minimum number of markers in the shot, I can deal with that, and factor it into the plan in case we need to do any medium shots.

How should I approach this?

Thanks,
Steve

[ssontech]

The number of balls is definitely an issue. I'd shoot for a dozen in frame at all times, probably some of them will wind up blocked etc and things never work out quite like planned. Beware pushing in or zooming in, and leaving the markers out of view. Also try to make sure that they aren't all on a back wall far away, some hanging ones are reasonable, some markers on the floor maybe too depending on the details.

[podmonger]

Thanks Russ, I'll pass that on.

Cheers,
Steve

[interactiveBoy]

This is the exact topic I was going to start. I have not yet purchased Syntheyes, but I will be next week. I tried the demo and it is fantastic!

I have a green screen shoot with a track and jib coming up and am trying to think ahead for what to do.

I had thought about the ping pong balls, and i'm concerned about them not being completely still (because they are so lightweight). I'm concerned that air currents from the HVAC system might cause problems. So I'm looking into either filling the balls with sand or using something else altogether. If i can find some cheap white rubber balls, that would be perfect.

I'll let ya know what I find.

[podmonger]

I've just done a test with cheap ping pong balls hung from twine, and they were quite steady. I don't remember HVAC being on, but we were in a large studio that can shoot schoolbus-sized objects, so maybe any breezes were out of range of our balls. They were not hung from the grid, but from a 20-foot sky-high and two head-high grip stands.

The balls were stuck to the string with red gaffer tape, and we found that tracking the corners of the red tape worked as well as tracking the balls.

A dolly move past a grip stand in front of the 20x20 foot green backdrop (hung to avoid having to paint the walls for the test) worked nicely with an automatic track. However, once we added dancers moving across the frame, they occluded the markers and made tracking interesting. I haven't had time to finesse the tracking and solving, but when I do, I'll post here.

If we did anything wrong, it might have been not having enough depth variation between the mid-ground balls and the tape markers on the greenscreen.

Steve

[interactiveBoy]

yeah. depth differentiation is my main concern. I'm planning on pre-stringing all the balls before the shoot, then spending a couple of hours on setup (hanging balls, taping walls and foor, etc)

How many balls did you end up using? I'm guessing we will be in the neighborhood of 60 for our shoot. (this does not count the markers on the wall and floor)

[mjackson]

Something that I've done very sucessfully in the past is putting pieces of green tape on your green screen. You might have to do a seperate key for the tape (maybe even some roto), but if the tracking information is more important then it is an option.

The tape should show up on your linear footage withouth issue, or a contrasted version of pre comped footage, but I wouldn't use a blue or orange tape since this will definitely require a pull that might fight with your foreground objects.

[oldmonk]