Greenscreen - tracker colours

[kamilkite]

Hi Guys,

I always thought that yellow trackers on greenscreen is the best solution because in 90% cases you can pull one key for both green and yellow.
Recently I saw that in Wrath of the Titans and Hugo they used red trackers on greenscreen and I wonder why. Because of better contrast/tracking issues???

WDYT

Regards

Kamil

[aaronber]

Yellow markers means that your green and blue channels are not affected by the markers and all of your marker data is in the Red channel. This is good when you have a 4:4:4 workflow but could come at a cost if your greenscreen isn't setup perfectly. Red markers are used because it gives you marker data in both the red and green channel, so there is a little redundancy in how much data you collect from the markers.

In the end it just comes down to the preference of the VFX supervisor, if you know that your plates are going through some really talented compositors and you want to be absolutely certain that they have the data they need you could go with red markers. If you have a setup that is bolted down and doesn't change and the luxury of testing out your setup to make sure it will work you could go with yellow markers.

[Gentle Fury]

I would say it's because Red is the opposite of Green so it will show up without fail. Now, keep in mind. Onset supervision is usually either nonexistent, or ignored. Most VFX are shot by people that have NEVER worked on a plate in their life. This becomes clear after seeing A) Green screen on a TV screen that is meant to be turned off...and B) Tracking markers all over a SET that has so much contrast the room itself is used for features more than the markers that now need to be removed (watch for those markers on reflective surfaces that need to retain reflections).

The thing I have learned in my years working on movies and television is that production either doesn't know, or doesn't care (most likely the latter) what is best for the artist using the plate and if there are track markers involved there will almost always be roto involved!

[kamilkite]

Hi,
My experience is that the trackers are not needed at all in most cases. There are usually a lot of "natural trackers" in frame anyway, like parts of the set. When you are using 3d trackers (like this one in Nuke) you don't need anything else.

[Invader777]

sorry I got on this one late... Tracking markers are an art. I have a couple of different preferences personally. white or red are great on greenscreen. (Except when passing behind the edges of the people/ obbject you are shooting... (Then they become a pain in the posterior and tend ruin the integrity of your final comp.). I like green tracking markers that are a stop or two different from the greenscreen. (They can still be tracked and keyed.) but they tend to fail when defocussed. (DOP's can be pretty stupid when it comes to greenscreen shots. They like to get the focus in camera.... not ususally the best idea. a sharp greenscreen is far easier to key., and can always [usually] be defocused later...)
The yellow marker idea is pretty cool. I must admit I didn't even think of it myself. channel repair would strip the marker right off and preserve a lot of detail... smart.
I guess a purple tracking marker on bluescreen would also do the job in the same concept.

but overall... just don't stick them behind what you shoot... and get them in 3D space, not just stuck on the back wall... if you manage these two things, you should be pretty good...
just don't let red tracking markers go behind frizzy orange hair... I still have nightmares about that job of mine.

[aaronber]

If you do an image search for tracking marker you will probably come up with something that looks like this : http://www.flickr.com/photos/alba/2505310839/

In my experience these are the worst, you can't key them and although they give you lots of detail up close if there is any motion blur they become ridiculous to keep a solid track on. Far away they don't have enough contrast, and out of focus they turn into circles. Give me a solid corner per marker to track off of, not 10. It makes logical sense to use something like this, but after using them for a bit I grew to hate them. Gaff tape x's are more useful, cheaper, easier to put up and take down, better for tracking and your compositors won't hate you.

For a good reference check out these guys:
http://www.stopp.se/lab/?p=1224

[MrMovie]

Great information, Aaron. Thanks for the post.

[zoostory]

Go to dragonlasers.com, get yourself a 90mW green laser and some grid defraction grating. Use a C-stand, aim laser from side angle (so as not to hit people) through taped on grating and make a nice green dot pattern on your screen. As mentioned above, repo as needed to avoid underlapping FG talent as much as possible. Esp on longer lens shots any tracker is annoying when it tramples into a soft edge.

This is my latest technique. Before that I used Green Gaff tape on Chroma Green screens and Blue Gaff tape on digi green screens. You'd be amazed at how LITTLE you need these days. But with tape, if the camera is down low tilted up even 3 degrees, get ready to run for a 20 foot ladder and get the AC to help point you to where those trackers need to be.

I worked on a show where a seasoned VFX super put red tracking markers on a blue screen, and the talent was in blue jeans, a blue sweatshirt, and a red vest. No joke. Don't do that

EDIT: Be very CAREFUL with the laser. Make sure it is defracted through the grating to dissipate the energy. Also make sure to alert everyone to not cross it or look at it. a 90mW and above can pop baloons and such! You can also try lower, like a 50mW, but it may not be bright enough dep on the amount of light on the screen.

[Gentle Fury]

Go to dragonlasers.com, get yourself a 90mW green laser and some grid defraction grating. Use a C-stand, aim laser from side angle (so as not to hit people) through taped on grating and make a nice green dot pattern on your screen. As mentioned above, repo as needed to avoid underlapping FG talent as much as possible. Esp on longer lens shots any tracker is annoying when it tramples into a soft edge.

This is my latest technique. Before that I used Green Gaff tape on Chroma Green screens and Blue Gaff tape on digi green screens. You'd be amazed at how LITTLE you need these days. But with tape, if the camera is down low tilted up even 3 degrees, get ready to run for a 20 foot ladder and get the AC to help point you to where those trackers need to be.

I worked on a show where a seasoned VFX super put red tracking markers on a blue screen, and the talent was in blue jeans, a blue sweatshirt, and a red vest. No joke. Don't do that

EDIT: Be very CAREFUL with the laser. Make sure it is defracted through the grating to dissipate the energy. Also make sure to alert everyone to not cross it or look at it. a 90mW and above can pop baloons and such! You can also try lower, like a 50mW, but it may not be bright enough dep on the amount of light on the screen.

LOL, you are lucky to get someone with a roll of red gaff tape willing to stick something on a screen.....not a chance of getting a laser array!

[zoostory]

LOL, you are lucky to get someone with a roll of red gaff tape willing to stick something on a screen.....not a chance of getting a laser array!

Well he was the VFX Super, so having gaff tape was his job Dude, you can build a laser array for less than $150 bucks.

[Gentle Fury]

Well he was the VFX Super, so having gaff tape was his job Dude, you can build a laser array for less than $150 bucks.

It's not about the money, it's about the effort...and in my experience, there is very little effort put into prepping shots on set for VFX....it tends to be, worry about it later. In a perfect world I 100% agree with you! I was VFX Sup on one project years ago and I made sure we didn't roll a single take until the set was prepped for later. It was the easiest footage I ever worked with.

[zoostory]

It's not about the money, it's about the effort...and in my experience, there is very little effort put into prepping shots on set for VFX....it tends to be, worry about it later. In a perfect world I 100% agree with you! I was VFX Sup on one project years ago and I made sure we didn't roll a single take until the set was prepped for later. It was the easiest footage I ever worked with.

Yeah I know what you're saying. Sometimes shows don't want a super on set because they don't want to pay... only to pay 3x as much in post. But then again, the shows arguments are that whenever they pay for a VFX supervisor, they usually find them hanging out at the kraft service table instead of working (so why pay?)

I supervise a lot, sort of fell in to it to be honest, but I care about the sum of the product being created immensely and feel that it is my duty to contribute as much as I can when I am on set, in prep, and in post.

I think a lot of this stems from a lack of understanding of what VFX are. To the laymen, the rules are confusing... it's easier to turn off and worry about it later. Other departments, like camera, have had a 100 years of language building, to the point where a writer or director can look at raw dailies and imagine how they will work in the future. They can read between the lines. With VFX, or a GS shoot, only very few can imagine the end result. What you get are a lot of nerves, bad communications, technical errors... and sometimes even apathy and neglect by tired crews that just want to make their day.

I believe that it's really up to us to fight the good fight and prove our worth. And over time things will get better as the language of what we do becomes more clear and younger generations move in to more meaningful roles. Optimistic perhaps?

[Gentle Fury]

Yeah I know what you're saying. Sometimes shows don't want a super on set because they don't want to pay... only to pay 3x as much in post. But then again, the shows arguments are that whenever they pay for a VFX supervisor, they usually find them hanging out at the kraft service table instead of working (so why pay?)

I supervise a lot, sort of fell in to it to be honest, but I care about the sum of the product being created immensely and feel that it is my duty to contribute as much as I can when I am on set, in prep, and in post.

I think a lot of this stems from a lack of understanding of what VFX are. To the laymen, the rules are confusing... it's easier to turn off and worry about it later. Other departments, like camera, have had a 100 years of language building, to the point where a writer or director can look at raw dailies and imagine how they will work in the future. They can read between the lines. With VFX, or a GS shoot, only very few can imagine the end result. What you get are a lot of nerves, bad communications, technical errors... and sometimes even apathy and neglect by tired crews that just want to make their day.

I believe that it's really up to us to fight the good fight and prove our worth. And over time things will get better as the language of what we do becomes more clear and younger generations move in to more meaningful roles. Optimistic perhaps?

I really hope it can one day come to that....but I have had so many shots that have no trackers, too many trackers, trackers that should never have been placed, green on tv screens that will be turned off, markers on reflective surfaces, no markers on 100% green screen, purple underexposed blue screen and yellow over exposed green screen, and small patches of green where they aren't needed and box lights where there should be green screen and needs to be comped over a dark env. I have dealt with so much bad footage...and created so many gizmos to help solve these problems it is now expected. Green Screen = problems. Hell, comp shot = problems. Thankfully,we get paid rather generously to solve these problems...so no big deal...and honestly....perfect footage is boring to work with! Problem footage presents a challenge....that's more fun for me!

[MrMovie]

@ Gentle Fury - that reminds me of a sign I once saw:

"We, the willing, working for the ungrateful, are doing the impossible. We have done so much, for so long, with so little, we are now qualified to do anything with nothing."