Building the Perfect HDV Key
Building the Perfect HDV Key
|Creative COW Magazine Extra |
|Tim Wilson, |
Boston, MA USA
©2007, Creative COW
|Article Focus: |
In the first of our Creative COW Magazine Web Extras, we begin with Stephen Smith's outstanding article on setting up an area for proper keying from the May-June 2007 edition. His article covers every option for setting up and lighting perfect keys. Here, we look at the best advice around The COW's online communities for pulling keys from HDV footage.
| In the first of our Creative COW Magazine Web Extras, we begin with Stephen Smith's outstanding article, Perfect Color Keys: A Checklist. You'll he a little ahead of the game for the magazine itself this time, as you can download it without registering for a subscription this time. But only until June 18, so don't delay! .
Of course, there's no reason why you shouldn't subscribe to The COW magazine already. It's fast, easy, and free. We've never sold our members' names for any reason, and we never will. And if you don't want any additional mail, every issue including back issues is available as a PDF. (Actually, most people get both the print and PDF editions. If you're outside the US, PDF is the only version available at this time.)
One of the things you'll find in the article is a string of great graphics of some of the keys Stephen has pulled for a show open we did. (We used one of those pictures for our title graphic, too.) Here is the keyed animation in action!
e expand on the themes of Stephen's article by focusing one of the stickiest subjects at CreativeCOW.net over the years: keying HDV.
By all means though, start with Stephen's article. He covers optimizing every option for keying backgrounds, from green paper to constructing a full green screen area in your studio. One of the most critical things you'll find in his article is specific advice for successful lighting, including an easy to understand illustration of ideal light set-up.
(This is the kind of information you need to subscribe to the magazine for.)
As you look through all the communities of The COW (and we have -- nearly a dozen of them discuss keying HDV), you'll find again and again that proper lighting is the "key" to a great key. Again Stephen's article offers the most comprehensive advice on this we've seen.
But what about the HDV format? Does it get in the way of a successful key? Not necessarily. Despite its similarities to DV, COWfolk have repeatedly found that HDV works better than DV for pulling keys. Here's a sample post, in this case about a workflow more common than you might think: shooting HDV for SD delivery. (As always, posts are edited for length and grammar.) Here's sam.mltn:
I've worked with HDV footage and it's way better than DV. Here's what I did. I brought in the sony HDV footage at full 1080i, sized it down to 720p and rendered an animation codec master. Pulled my key, then output a 720p h264 codec quicktime for playback on a macbook pro for a trade show directly to a 40" plasma through the dvi connector plugged into the macbook. Then rendered a standard widescreen dvd for delivery to the client. The difference between this project and a similar one that I did last year was amazing.
That's quite the torture test for a supposedly fragile format. For details, I asked Tim Kolb why HDV works better than DV for keying, and here's what he had to say:
I know that many will scream blasphemy, but it's not all that hard to figure out frankly. The chroma samples in DV are arranged 4:1:1, which means that a single color difference sample has to be spread over 4 pixels in a horizontal row. HDV's 4:2:0, while still only one color difference value for four pixels, has the pattern in a 2x2 block.
Simply, that means less potential for error. And of course an HDV frame simply has more pixels. Looking at the horizontal pixel counts for example (with rounded numbers), DV has a .4% potential error, compared to HDV's .07% -- a truly remarkable difference.
So that's why HDV works better than DV. Let's look at some of the ways that people are using to actually pull those keys.
Stephen's article in The COW magazine emphasized that, if you light properly, any software will work just fine. That said, a number of specific options have popped up.
Much of the keying discussions have, naturally enough, taken place in the Adobe After Effects community. Most of the attention has been paid to Keylight, an Academy Award-winning keyer from The Foundry, with built-in spill suppression. It's a free upgrade for AE Professional v.7 users, and included with recent purchases of AE 7 Standard, where you'll find it in the third-party options on the install disk. (We haven't heard yet how it will be included with AE CS3.)
It's hard to avoid starting with the option included for free. Andrew Shanks was kind enough to remind us of Barend Onneweer's close-up look at Keylight when it was first added to AE, with version 6.
Several people mentioned that Andrew Kramer did a great Keylight tutorial that you should definitely check out. That tutorial is also included with Serious Effects and Compositing vol. 1 in The Creative COW Master Series. It's one of the best-selling AE disks ever, and you should definitely check that one out too.
The point is that Keylight is free for many recent AE owners. It works great.
The next most frequently mentioned option is Boris Continuum Complete. Boris's keying algorithm has long been praised as one of the very best for DV, but it hardly stops with DV. It also doesn't stop with After Effects: BCC is also available for Adobe Premiere Pro, Apple Final Cut Pro, Apple Motion, Autodesk Combustion, any high-end Autodesk systems that feature the Sparks API, and Avid's Media Composer family of NLEs (MC, Symphony, Xpress). Jeremy Garchow (JeremyG) and Walter Biscardi are among the COW leaders who turn to BCC's keyer first.
After that, you'll find many COWs turning to the product formerly known as Serious Magic Ultra. You'll find it included as Adobe Ultra with the upcoming release of the CS3 Production Premium Suite. Adobe's Chief Strategist for Dynamic Media developed Ultra while at Serious Magic, and before that, Trinity Play and the Video Toaster. He notes that Ultra was specifically designed to key difficult footage. The COW's Paul Meyers is one of the folks who can attest to this. He says it very simply: "Want good keying? Get Serious Magic Ultra."
Harm Millaard is equally blunt: "Ultra, IMO[is] the easiest and best chroma keyer there is."
One of the choices that has elicited an especially strong response is the one built into Matrox Axio. You'll find plenty of quotes to this effect, but here's an especially compelling one from Ron Shook:
I went to my old friend Larry Sherwood's Axio demo at Lyn Norstad's digs in Chicago. Larry had some green screen Sony Z1 HDV footage that he'd shot outside against a fabric background that was as garish as any chroma key footage I've ever seen. The screen was chock full of folds, shadows, lit by direct, harsh sunlight with no bounce, plus it was undulating in the breeze. Larry said that after looking at the footage, he almost didn't even capture it to try in Axio. When he did, he hit the one button chroma keyer and then said, "Oh, my God."
The chroma keying, color matching, and primary and secondary color correction are second to none, IMO, and all real time at finish quality, even with HDV. Zowee!
(Platform note: Axio and Ultra are both Windows-only, Boris Continuum Complete and Keylight are cross-platform.)
So there you go. Our "COW Magazine Extra" is a speedy round-up of The COW's Collected Wisdom on keying HDV. But do start with Stephen Smith's great article. "Perfect Color Keys: A Checklist," in the May-June issue of Creative COW Magazine. If you miss the unregistred download before June 18, go ahead and sign up for a free subscription. We're already at work on the next issue, and we know you won't want to miss a thing!
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