Pulling keys is usually a royal pain, especially if you’re working with footage that someone else shot. The lighting isn’t right, the key isn’t simple, garbage mattes have to be keyframed, and spill filters have to be tweaked. It was a lot of work—until now.
I’m writing this after having just run a new keyer plug-in through its paces. It’s Phyx Keyer, developed by PHYX, Inc., and it runs on the FxFactory plug-in engine.
It can function as a plug-in to Adobe After Effects, Apple Final Cut Pro (FCP), and Apple Motion. When installed via the FxFactory application, the Phyx Keyer package includes five plug-ins: Keyer, Lightwrap, DiffKeyer, Screencorrector, and Despill (Figure 1, below). All the plug-ins have a Help button that will launch your web browser into the appropriate Phyxware.com page.
Figure 1. The five Phyx Keyer plug-ins, clockwise from top: Keyer, Lightwrap, DiffKeyer, Screencorrector, and Despill
This is the first thing I was impressed with: having Help actually built into the plug-in itself. I wish all plug-in developers did this. Being able to save my settings as presets in each of these plug-ins could make postproduction on larger projects much easier too. Because the presets are independent documents, saved to any location I want, I can move and share them between edit bays—another feature I wish more filters adopted.
I tested these plug-ins in both Final Cut Pro 7.0.2 and Motion 4.0.2 using Snow Leopard 10.6.4 on a Mac Pro running an ATI Radeon 4870 graphics card with 16GB RAM. I was also viewing my output through an AJA Kona LHi card, on an FSI LM-2450W production monitor. I wanted to be able to see as clearly as I could how clean or dirty this keyer would be.
I’ll run through these filters in the order I used them. Naturally, I started with Keyer. The first thing I noticed was the lack of controls. I was taken aback at first, but once I started to tweak the key, I was amazed at how much I could do with so little. This is a very simple keyer to use, and I was really impressed with the lack of time I had to spend with it, even on the first attempt, learning it from scratch. Being able to select my Chroma Reconstruction between 4:4:4, 4:2:2, and 4:1:1 was nice. Having three selections in the Keyer Types section is handy and makes things really simple. There is YUV Difference (use the standard color palette and eyedropper to chose your color), Channel Keyer (what you’d normally use for a blue/greenscreen shot), and a 3D Keyer (for work in 3D spaces).
Each of these selections brings up a set of controls. In each case, the controls are few but powerful. Nothing else is needed. I can also switch between my Output and my Alpha Channel to judge how cleanly my key is working. Comparing the same key in both FCP and Motion, I don’t see much difference—if anything, the key is cleaner in Motion, but only very slightly. They both look really nice and very clean.
Like Keyer, Despill is very simple, but it works very well. Choose either Green or Blue as your Method. Adjust the Despill Amount, and that’s it. I wish it were a bit stronger, but it did a great job desaturating the green from my subject, not just around the edges but across the whole image, which I like. Easy, simple, and effective—this is a well-developed filter.
I ran my greenscreen clip against four different backgrounds in order to test the Lightwrap filter (Figure 2, below). This is a great filter that lets you drop your background image into an image well in the filter. Then, you can adjust the Blur, Width, and Amount of the wrap. What this means is that it’s using the background image to “wrap” lighting around the darker areas of your keyed subject.
Figure 2. Keying in different backgrounds with the Lightwrap filter
I found this to be a great help in making the subject fit into the background lighting more constantly. Again, it’s very simple, powerful, efficient, and effective. Those three adjustments were all I needed to complete the keying on my shot. Quick, easy, and clean.
Clean Plates and Shadows
If you need to go further in your keying work and get more sophisticated, here’s where Phyx really shines. The final two filters use a Clean Plate. A very simple explanation of a Clean Plate is when you shoot your scene without talent (Figure 3, below, top left), then shoot it a second time with talent (Figure 3, top right). The shot without talent is the Clean Plate. These Clean Plates are used by compositing software to help key talent out of the background, by comparing the background Clean Plate to the foreground shot, and removing everything that doesn’t match. A Clean Plate is used in both the Screencorrector and DiffKeyer filters.
Figure 3. Comparing the background Clean Plate to the foreground shot (top left and right), using Screencorrector to smooth out the greenscreen (bottom left), and killing off shadows with the DiffKeyer (bottom right)
Here is where the biggest enemy of keying work becomes very apparent. Shadows should be avoided at all cost when shooting blue/greenscreens. Take as much time and effort to kill off shadows as is necessary, and you’re home free. In keying, shadows are not our friends!
The Screencorrector is a nice plug-in for smoothing out your screen. It won’t fix drastic shadows, but it will smooth out reasonable areas where your screen isn’t lit evenly. If you have to work with poorly lit screens, this would be a very quick and easy way to smooth the green/blue background out. Apply the filter and drop your Clean Plate into the image well; Screencorrector does all the work automatically (Figure 3, bottom left).
You can tweak the color that you’re smoothing with Screencorrector using the standard color palette and eyedropper. But right off the bat, it works simply and effectively.
Finally, there’s the DiffKeyer, which creates mattes using a Clean Plate. Again, shadows create a problem with Clean Pates in chromakeying work, and they’ll show up here more than anywhere (Figure 3, bottom right). If you’re really trying to key out your talent, light to kill off shadows!
The DiffKeyer is as simple as the other filters in the Phyx Keyer package, and it’s just as effective. Once you drop your Clean Plate into the image well, you can adjust the highlight and dark areas of your matte, overall brightness, and contrast. You can also switch between the Output and Alpha channel to better determine how clean your matte is.
All in all, the Phyx Keyer package is a deal at $199, considering all the tools you get with it. Is the keyer better than others, such as Motion’s Primatte RT? It’s not only as good but also a bit easier to use, and it comes with other tools (the Lightwrap, Screencorrector, and DiffKeyer) that are useful for serious keying work.
A major difference is that when doing spill suppression, Phyx seems to desaturate the greens in your subject image, while Primatte changes the overall hue to kill off the green. These are different approaches with different effects, and I like being able to choose the approach that works best for each individual key. Phyx also lets you save your settings as mobile presets—a huge plus.
All in all, Phyx Keyer is a great bargain and a very well-developed set of useful and easy-to-use filters that are effective and fast. Visit the Phyx site at www.phyxware.com or Noise Industries at www.noiseindustries.com for more information, tutorials, and ordering information.
Ben Balser (benb at bbalser.com) is an Apple Certified Master Trainer and Support Professional based in Louisiana. He produces media, consults for studios, and teaches media production nationally.