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ThomasDG
Participant
January 10, 2018
Answered

Green screen Tracking Markers

  • January 10, 2018
  • 1 reply
  • 8423 views

Hi,

I need tracking markers for on my green screen but i see a lot of variety, some are just green pieces of tape others are white with black.

I just don't know which one i need cause i don't know what the differences are..

So i hope someone can help me with this

Kind regards,

Thomas de Groot

This topic has been closed for replies.
Correct answer Rick Gerard

The kind of markers you use depends on the shot you are trying to pull off. Motion Stabilizing requires areas of detail so a simple darker colored square may not be as good as others that have more detail. Sometimes just using a couple of pieces of tape to form a + is all you need.

Camera tracking is an entirely different problem. If you have a panning move with the camera then you will not get depth information so things can get pretty tricky if you are trying to simulate things like a virtual set. Handheld walking, dolly shots, tracking shots, basically, any shot where the camera is moving more than a couple of inches require multi-plane areas with detail so you are not likely to achieve a good camera solve if you just have a bunch of markers on a flat green screen 6 feet behind your actor. You will need to put some boxes in the shot that can be tracked and make sure there is enough detail in those pieces of fixed geometry to get some good parallax and perspective data so the camera movement can be solved.

It would help us help you figure out the most efficient solution if you could provide a detailed description or even a storyboard of the shot you are trying to create. There is no one trick solves all problems solution available. Most of the time I do not use any markers on the green screen, I just put something in the shot that has a lot of detail that I can easily roto or mask out. Whatever you decide to do you need to make sure that you do not have tracking markers anywhere near any edges that are going to be hard to key. A tracking marker directly behind someone's beautiful head of wavy hair is going to give you a ton of problems. A tracking marker close to an edge that has a lot of green spill is also going to cause you a lot of problems. If you are doing a lot of camera movement then you are going to have to be very careful blocking the shot and setting up the tracking markers to prevent causing post-production problems that can easily spoil a shot completely by making it nearly impossible to pull a decent matte without a ton of hand work.

1 reply

R
Community Expert
Rick GerardCommunity ExpertCorrect answer
Community Expert
January 10, 2018

The kind of markers you use depends on the shot you are trying to pull off. Motion Stabilizing requires areas of detail so a simple darker colored square may not be as good as others that have more detail. Sometimes just using a couple of pieces of tape to form a + is all you need.

Camera tracking is an entirely different problem. If you have a panning move with the camera then you will not get depth information so things can get pretty tricky if you are trying to simulate things like a virtual set. Handheld walking, dolly shots, tracking shots, basically, any shot where the camera is moving more than a couple of inches require multi-plane areas with detail so you are not likely to achieve a good camera solve if you just have a bunch of markers on a flat green screen 6 feet behind your actor. You will need to put some boxes in the shot that can be tracked and make sure there is enough detail in those pieces of fixed geometry to get some good parallax and perspective data so the camera movement can be solved.

It would help us help you figure out the most efficient solution if you could provide a detailed description or even a storyboard of the shot you are trying to create. There is no one trick solves all problems solution available. Most of the time I do not use any markers on the green screen, I just put something in the shot that has a lot of detail that I can easily roto or mask out. Whatever you decide to do you need to make sure that you do not have tracking markers anywhere near any edges that are going to be hard to key. A tracking marker directly behind someone's beautiful head of wavy hair is going to give you a ton of problems. A tracking marker close to an edge that has a lot of green spill is also going to cause you a lot of problems. If you are doing a lot of camera movement then you are going to have to be very careful blocking the shot and setting up the tracking markers to prevent causing post-production problems that can easily spoil a shot completely by making it nearly impossible to pull a decent matte without a ton of hand work.

T
ThomasDGAuthor
Participant
January 10, 2018

-Topicstarter-

Thanks so much! I'm remaking this music video Katy Perry - Chained To The Rhythm (Official) ft. Skip Marley - YouTube

So the actors are basically standing in front of a green screen that goes around a corner. So like _| that haha.

I'm gonna edit most of the people out of the original so my actors are going to replace them. (Or with photoshop or with camera mapping)

I never worked with markers before but i realized with the last one I've done, the background didn't move and the actor did so it looked really weird.

R
Community Expert
Rick GerardCommunity Expert
Community Expert
January 10, 2018

Well, there are a zillion shots in that video, most of them are on set and not green screen. Are you wanting to use that video as the background and replace some of the people in the video with your own actors? If so you are looking at a huge project involving thousands of hours of post.

Either point me to a specific time in the video for the shot you want to do or give me more detail.

I did a shoot recently where an actor walked around a corner, I followed the actor with the camera, there was a portable green screen just around the corner held by a couple of assistants, and then we transitioned to a different city so it looked like my actor went around a corner and ended up across the country. The entire line up and the composite was done with no camera tracking. I used Stabilize Motion on about 40 frames of the shot right when the actor walked around the corner and passed in front of the green screen so I could line up the shots in post, then some careful roto was used to complete the transition to the next location and the transition was made. The most difficult part of the whole shoot was keeping my actor exactly the same distance from the camera in both shots so the perspective would not shift when we did the match cut from one street to another.

I did another shot not too long ago where an actor needed to be placed in a factory after the fact. We took careful measurements in the factory and drew a floor plan so we could place some props on the green screen stage for the actor to walk behind, recorded the path of the camera carefully by having tape marks on the floor for the camera operator to follow, then duplicated the layout on the stage and shot the greenscreen footage. In this case, we shot the background plate in the Factory at 60 fps so we could have more control over the timing of the shot and match up the timing with the green screen footage, Stabilize Motion was used to get things to line up, then the composite was made. After the composite was successful I put the motion back in the background plate, added it to the motion stabilized foreground (green screen) plate, then Camera Tracked the entire rendered composite so that we could add some graphics and   a new piece of equipment to the shot using CGI.

My point in these two stories is that it takes a lot of careful planning to pull off moving camera composites. Each shot must be analyzed and a plan made and carefully followed to get things to line up properly. You can't just throw a couple of tracking markers on a green wall and match up two different moving shots or put folks in a scene without some very careful planning. The most important part of any of these kinds of effects shots is keeping the distance and angle from the camera to your actors the same in both shots. If the actor is supposed to be 10 feet from the camera in the right third of the frame in the composite, then the actor needs to be 10 feet from the camera and in the right third of the frame when you shoot the green screen shot or you can't properly line up the composite.

I'll try and help if you give more details. Expect others to jump in also.

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