Jump to content


Photo

shooting a chroma key suit under difficult conditions


  • Please log in to reply
6 replies to this topic

#1 Sherwin Akbarzadeh

Sherwin Akbarzadeh
  • Basic Members
  • PipPip
  • 22 posts
  • Cinematographer

Posted 06 January 2011 - 07:43 AM

Hi,

I'm in pre-production on a project which makes heavy use of chroma key suits. The tough thing is that I'm shooting it outdoors in bright sunlight. After initial tests with industry standard lime green suits I discovered that they reflect too much light and the result is washed out and basically unkeyable (luma keying is messy too). Is anyone aware of chroma key suits in alternative, duller fabrics that do not reflect as much light?

Official chroma key suits seem to come only in shiny green, lime or blue so I had to think laterally. This COULD be an option:

http://www.milanoo.c....it-p16069.html

And yes, I am aware that it was built for something other than chroma keying!

Think it'll float? I'm opting for magenta because it clashes least with my background.

Anyway, if anyone has ever used a chroma key suit under bright sun, I'd love to hear from you!

Cheers,
Sherwin
  • 0

#2 Scott Fritzshall

Scott Fritzshall
  • Basic Members
  • PipPipPipPip
  • 584 posts
  • Other
  • Los Angeles

Posted 06 January 2011 - 06:22 PM

You generally don't end up actually keying people in suits like this; you generally end up using them to delineate the areas that you'll be removing by other methods. If the problem is that they're reflecting too much green light onto the rest of the scene, maybe you can replace it with a black suit.
  • 0

#3 Sherwin Akbarzadeh

Sherwin Akbarzadeh
  • Basic Members
  • PipPip
  • 22 posts
  • Cinematographer

Posted 07 January 2011 - 02:30 AM

thanks for replying scott. No, the problem is that the suit gets washed out under bright sunlight. I'm looking at having a suit custom made with 95% cotton / 5% spandex fabric. Much duller. This is a 15minute movie. I don't want to rotoscope it!
  • 0

#4 Scott Fritzshall

Scott Fritzshall
  • Basic Members
  • PipPipPipPip
  • 584 posts
  • Other
  • Los Angeles

Posted 07 January 2011 - 03:34 AM

Well, what exactly is going on in these shots? What will you be replacing the suited actor with?
  • 0

#5 Sherwin Akbarzadeh

Sherwin Akbarzadeh
  • Basic Members
  • PipPip
  • 22 posts
  • Cinematographer

Posted 08 January 2011 - 03:52 AM

Alright, I'll just go ahead and tell you exactly what this project involves. I am animating the character's bodies with various imagery but often the silhouettes are filled by the defocused image of their background - as if their bodies behave like a prism that defocuses what we see through it. For this imagery, I'll shoot a defocused clean plate after every take. The easiest way to make sure the defocused footage matches up with the alpha footage is to keep both shots static on a tripod but as I'd prefer a handheld feel so I'm experimenting with motion tracking options. My idea is to shoot the takes with the suits handheld and motion track the movements in post, shoot the defocused clean plate on a tripod and attach it to the tracked motion so that things vaguely match. I figure that with defocused image, I do have some margin for error since the forms are blurry. My main question is whether I need to place markers on my actors or the background to facilitate motion tracking. Once chroma keyed, wouldn't the silhouette provide a sharp enough point somewhere to motion track off? But the sensible option is probably to place a marker on the scene. Would some brightly coloured gaffer tape, which I key out and replace with a clean slate, do the trick?

I'm still not sure whether to go with red or magenta suits (which will give me a lower IRE reading at the same exposure?)

I'm sure you envisage problems so i'd love to hear about them!

Cheers,
Sherwin
  • 0

#6 Scott Fritzshall

Scott Fritzshall
  • Basic Members
  • PipPipPipPip
  • 584 posts
  • Other
  • Los Angeles

Posted 08 January 2011 - 03:28 PM

Regarding camera tracking, you won't really be able to use your actors for tracking points since they will be moving. The math for solving camera movements depends on the assumption that all of the points you give it are totally static. Most of the time, you can track off of objects and features in the scene, but sometimes you may need to place your own tracking markers at key points. You want distinct features or points of contrast at multiple planes of depth, so that you get some parallax. You won't really be able to key the markers out, you'll need to paint them out or track or project patches over them.

When you shoot your defocused clean plate, you should probably move the camera back or use a wider lens, so that you get enough of the scene to cover the full range of camera movement. Depending on how the camera moves, you may possibly need multiple clean plates that you stitch together.

The other option is to actually paint the performer out in each shot, which would give you an image that already moves properly and matches, that you could then defocus yourself.

As for the suits, you can certainly try to find a suit that exposes better, but rotoscoping is pretty much inevitable. You're never going to get a perfect key off of something that has contours and uneven lighting and moves around a lot. Even if you can get a pretty good key, you're going to have to clean it up with roto.
  • 0

#7 Sherwin Akbarzadeh

Sherwin Akbarzadeh
  • Basic Members
  • PipPip
  • 22 posts
  • Cinematographer

Posted 09 January 2011 - 07:05 AM

Thanks for your help Scott... I knew tracking points had to be on stationary objects - not sure what drugs I was on earlier... Your suggestions about getting a wider shot for the clean plate is a good one - I figure I can get away with a bit of scaling up in editing given that it's a soft defocused image. I'm having the suits custom made, as soon as i decide whether magenta or red is the best option.....

Anyway, thanks for talking me through this one. All the best with your projects.

Sherwin
  • 0


Broadcast Solutions Inc

rebotnix Technologies

Visual Products

Aerial Filmworks

Gamma Ray Digital Inc

The Slider

Ritter Battery

Wooden Camera

CineTape

Abel Cine

Metropolis Post

CineLab

Media Blackout - Custom Cables and AKS

Glidecam

Opal

Tai Audio

Paralinx LLC

Willys Widgets

Technodolly

Rig Wheels Passport

FJS International, LLC

Wooden Camera

Broadcast Solutions Inc

Willys Widgets

Rig Wheels Passport

CineTape

Opal

The Slider

FJS International, LLC

Media Blackout - Custom Cables and AKS

Visual Products

Abel Cine

Gamma Ray Digital Inc

CineLab

Paralinx LLC

Tai Audio

Aerial Filmworks

Technodolly

rebotnix Technologies

Ritter Battery

Glidecam

Metropolis Post