Green Screen with the EX1

basspig

basspig

Veteran
I shot an experimental video to test out a new training concept that a friend of mine wants to develop, and we threw together a cheap and dirty setup last Saturday and did a shoot.

The green screen consisted of 2 yards of fabric from Joann's (a fabric and crafts store), some 1x1 ballastrade to make a frame, a couple of clamp on work lights with CFL bulbs and our trusty EX1.

I have tried chromakey before with HDV cameras and Adobe Premiere's native simple keyer and the results were unusable. I would have to move to Adobe AfterEffects to use Keylight 1.2 to get a decent key.

So here I was, shooting our test footage against this piece of fabric, stretched over a wooden frame, hung from our studio ceiling. The fabric contains a visible weave (it's maybe 80 threads per inch, barely), although it's pretty much pure green.

I adjusted the illumination with the aid of the EX1's 70IRE zebras and found that even a 1º shift of angle of either lamp made a difference in the consistency of coverage, so I was able to tweak the lighting far better than by eye alone.

Then we shot some footage, and I brought it into Premiere. To my surprise, I was able to pull a pretty usable key with just the green screen key filter.

One more thing I discovered is that you can use Skin Tone Detail and set the phase to smooth bumps in the green spectrum, so I was able to soften the weave pattern, both by Skin Tone Detail and by short focusing the lens on the subject in front of the screen.

For kicks, I took the footage into AE and dragged the Keylight filter onto it. I only needed to click the eyedropper on the green background to instantly pull a perfect key. I needed to do nothing more. It was perfect as-is.

Chromakey with the EX1 is so easy and effortless. Very pleased!
 
Since I have a business partner (to whom the idea belongs), I'm not at liberty to divulge the concept. It's in its very early stages of development. In fact, this weekend, we're going to put our carpentry hats on and build a jig that will make it possible for us to do this with more precision and speed. I wish I could be more specific about it, but I'm not the sole party involved with the project.
 
The key looks great, though I thought the studio lighting was a bit dim on the shadow side of the girl. I would expect a bit more ambient light in the real outdoor scene.
Also, was the boat footage shot with a different cam? I noticed halos that I have only seen with earlier HD cam generations. Either that, or the white/black limiters weren't used.

I myself am trying to figure out how to use Keylight in Premiere. I was able to copy the Cycore plugins from AE to PPro, but doing the same with Keylight's plugins folder yielded no availability. Premiere is realtime with effects and EX1 footage, but AE only does about 3fps, making it impossible to work with.
 
uhm I actually had trouble seeing which part of the video was the actual keyed part! ok so it was the girl. great job
 
basspig said:
The key looks great, though I thought the studio lighting was a bit dim on the shadow side of the girl. I would expect a bit more ambient light in the real outdoor scene.
Also, was the boat footage shot with a different cam? I noticed halos that I have only seen with earlier HD cam generations. Either that, or the white/black limiters weren't used.

I myself am trying to figure out how to use Keylight in Premiere. I was able to copy the Cycore plugins from AE to PPro, but doing the same with Keylight's plugins folder yielded no availability. Premiere is realtime with effects and EX1 footage, but AE only does about 3fps, making it impossible to work with.
Click to expand...

All shot with an EX1. I made the mistake of giving a negative value to the crispening level when shooting Cindy's standups, hoping for a slightly softer edge. I should have left it at zero. Reinforces my usual rule of "shoot it straight and clean".

The background plate was shot with an HVX.

AE requires a great deal of RAM and fast processors to work in real time. Even then, it's only if you have it render a RAM preview first. I have an 8-core Intel Xeon Mac with 10 gigabytes of RAM. So it's fairly quick but not real time.

Keylight might be for AE only so that's why it's not working for Premiere. It's the same if I tried to use some of Commotion's plug-ins with AE. It shows up but doesn't function.
 
rrrobb said:
uhm I actually had trouble seeing which part of the video was the actual keyed part! ok so it was the girl. great job
Click to expand...

When no one says, "wow, that was a nice green screen job" you know you've done a good job. Just about everyone who saw the show thought it was real.

When the talent first saw she was going to be shot against green screen her first thought was "oh no." Then she saw the first test shot during setup, and she said it was the best green screen she had ever seen -- and that was just a quick, rough test comp with Keylight.

BTW, the screen is illuminated at 50%. I used to have it at 60% until a DP here recommended going lower for more color saturation. It also helps reduce the risk of spill.
 
Ah, I guessed right on the background plate--I kept thinking "with the fringe/halos around the edge of the boat, that can't be EX1 footage" and you've confirmed my suspicion.

I thought the key you pulled was great. I do think that you needed a bit more fill on the left though, to make her illumination match better with the illumination in the background plate. That was the only thing that keyed me in to the fact that she was keyed. :)

Ever since Premiere 3.2.0 came out, we've discovered it gives realtime playback with unrendered effects on EX1-based projects. I never used to color grade because it would take forever to render and would not play back unless I rendered it, but nowadays, we've been stacking filters like sharpen, color correctors and anti-alias on various clips and Premiere just chugs along at about 40-50% CPU utilization on our quad core workstations at 3.5GHz. It's been a beautiful upgrade. I just wish Adobe would tweak AfterEffects so that it can do that too.

In the meantime, we do most of our rough experimental keying in Premiere, because of the realtime operation it provides. If it had Keylight 1.2, it would be a fantastic combo.
 
Just did an interesting corporate shoot this week pulling a super clean key with the EX1. The client brought in a new Apple MacPro 8 Core full tower into the studio and hooked up the RGB from the EX1 so we were pulling video directly off the CMOS chip. That Apple is so quiet we had no problems with audio like we do even with laptops in the studio.
In the Apple was a new Intensity Card to capture the video to two internal hard drives that were stripped with Apple's Drive utilities for RAID 0. The video flow didn't even make this set-up break a sweat.
Then we used DV Garage's "Conduit" to do the keying. Conduit is a nodal compositor that actually sits inside of Motion 2 and Final Cut Pro 5.1.2. Nodal compositors provide a unique flow-chart approach to compositing. Rather than thinking in layers, each node applies an operation. This approach is very popular in high-end facilities because it provides a very open ended way to create composites that are customized to each challenge. It was amazing... and an absolutely clean key in 1080/30p. This was a real break thru for use since as we all know, chromakey is more of a VooDoo art than pure science. If I get a chance, I'll get some shots up... Frank Casanova, The Studio Center.
 
I wouldn't say it's voodoo at all. Chromakey is a very exacting process--if you don't have a narrow range of green RGB values and a good color subsampling resolution, it will be impossible to pull a clean key. Sure, there are tools that can blur the edges and reduce the appearance of jaggies, but there's no magic in them--just pure mathematics and science.
A good key comes from a good camera system, an operator who knows what the process requires for high quality results and a screen that is the right shade of green, uniformly lit, with no spill or shadows from the subject. It's all in the equipment and setup.
 
All very true Mark. I've always said "Things are easy... When you know how!" I guess that's why I keep a couple of chicken bones and a rabbit's foot in my pocket...just in case ;-)
 
Mark is right about the need for precision with the background color.

Sometimes you see examples of where a composite was done with a problem screen, but that's not the best way to get the best results.

Keying software depends on seeing a unique color or range of colors. And if that range gets too wide then it starts to select part of the subject, too. That's when the talent starts to lose their hair, parts of their hands, develop holes in their bodies, etc.

And everything from having a clean lens to doing anything possible to avoid spill or green contamination helps make the process easier and more seamless. And another tip: turn off any in-camera sharpening. The outlines sharpening circuits create can be a terrible problem in post.
 
Nice job

Nice job

Dean,

Super job. I wouldn't have noticed you used a key unless I was looking for it.

I personally think the underexposed right arm area adds to the illusion that she's out in bright sunlight.
 
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magicdavek...

Thanks!

This process saves us in a lot of ways.

Our talent is available only in the evenings. The weather can't be counted on to be picture perfect when we need to shoot. And it solves the problems of waiting for sun, waiting for airplanes to pass, waiting for the background to clear, and hoping to avoid attracting unwanted attention.
 
A very good keying job. Only one thing: I think the composition would look more real, if the background would have been shot a little bit out of focus.
 
I thought about doing a bit more blur but it wasn't looking quite right. The DOF from that camera tends to be deep at that focal length, and it was more believable with just a small amount of gausian blur applied.

One comment someone said was that while it looked real, he wondered how the host could look so good for an outdoor shot. That's something else to look at carefully when doing this sort of composite. In "real life" there's often something that makes the shot look just a bit less than pristine.
 
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