Motion Tracking with Green Screen Questions

[ChadN]

Hey all,

I've done a decent amount of chroma key in the past, but i'm looking to add some camera movement. I'll need to motion track, and i had a couple of questions.

What color tape would be best for the tracking points? I've seen everything from yellow to light green to red in photos from film sets.

Also would i get to simply key out the track points along with the green screen, or will i be getting in to a lot of masking and nearly rotoscoping the actors out if the track points don't key out?

I get the general idea of doing a motion track and all that, i'm just not sure what color tape to use for the points and how that would effect keying and tracking. Any advice would be great! Thanks.

 

[clang]

Keying out the tracking points is theoretically possible, but given that one layer of keying is difficult enough, I suspect that two layers would be tempting fate, unless you have very limited colours in your foreground action. If you want to try this option, I'd experiment with another shade of green, as that would seem less likely to have colour spill etc problems than wildly different colours (e.g. red points on a green screen). The potential downside of using similar colours is that it increases the chances of points occasionally being difficult to see.

I believe that masking is commonly used to make the tracking points disappear in post - fairly easy if the foreground action isn't too close to those points (as the masking can be fairly loose), but occasionally tedious when the masks need to be pixel perfect.

 

[msorrels]

Hollywood Camera Work VFX For Directors (a video training course) advocates using the same color as the screen but 1/2 stop brighter or darker. Then two separate layers of keying and some crude masks around the markers to keep the highest quality keying. I have only done some small tests with this, but using a different shade of green seemed to work fine for the tracking and keying it wasn't that difficult. You are going to have to do some masking since the perfect key settings for one green is likely to blur out hair/edges on the second green's perfect settings. But tracking can track the markers fairly well and the mask just has to be close most of the time (parent the mask to the track). Another tip: no circles/dots for markers. Trackers need edges. Dots don't always change enough when the camera moves so they can become hard to track, especially moving in and out. Anything else is better, L-shapes, Crosses, Triangles, even squares.