Power Windows: Coloring Correction with Training Wheels

Like a lot of people with Final Cut Pro or After Effects, I’m trying to become a crack colorist in the privacy of my own home. It’s unlikely to happen anytime soon as I just don’t have the training or the time to take on a second full time career. But—that doesn’t mean I can’t do a little bit of damage to my own footage when I want to experiment. Or when I’m too cheap to hire someone else to do it.

There’s been much discussion on the Cinematography Mailing List about rookie colorists and why it’s a bad idea to try to do these things yourself on a wing and a prayer, but I figure the more I work on my footage the more I’ll learn about giving others the kinds of images that they can improve on my behalf in the future. I’ve done the same thing editing my own footage, and I’ve learned a hell of a lot not just about shooting for editors but also how to fix the kinds of mistakes that just happen on sets when we’re working against time and budget.

I don’t have a color critical monitor, and as much as I’ve tried to calibrate my Apple Cinema Displays to look something like what I might find on a badly tuned TV set in a third world nation, I can’t quite get close enough to feel comfortable. If I’m working with a piece of footage that’s been horribly screwed up in post by someone else (I once shot some jeans spots where the client decided the whole thing should have a blue cast because, well, jeans are blue, and isn’t that a good enough reason?) I can bring it back to normal, but creating rich sophisticated looks on a questionably-calibrated computer LCD is a little frustrating.

The one thing I can’t screw up too much is luminance, and the single most beneficial thing I can do to my 8-bit HD footage is to pop in a Power Window and reduce bright unclipped areas that I couldn’t control during shooting. This is super simple in a telecine suite on someone else’s dime, but where I live and work HD footage is made on the set and never touched again. That’s fine, we do good work anyway, but it’s nice to have the opportunity to take footage to the next level. And since I’m only affecting brightness, which I can judge reasonably well on a computer screen and via waveform, I’ve got a lot more confidence controlling luminance alone than if I decided to cool the shadows and warm the highlights with any degree of finesse.

I’ve got Digital Film Tools 55mm, Apple’s Color, and Magic Bullet’s Colorista, and all can do vignettes (frequently called Power Windows because that’s they’re designated on a high-end Da Vinci color corrector). So far, for ease of use, Colorista wins hands down. It’s incredibly simple to quickly create a Power Window.

In this shot, from a Microsoft Zune spot shot on a Varicam (with a Pro35, Zeiss Super Speeds, and while riding a Steadicam operated by Tim Bellen) I’ve always been bugged by not being able to cut the laptop brightness down a bit. We were shooting in a cafe in Santa Cruz, and our morning ritual saw the crew standing around on top of a train trestle for two hours waiting to shoot the first shot while the day’s creative was re-written. As a result we ended up in this cafe shooting day/interiors after the sun went down. It ended up being a 17 hour day, and at some point our mission became doing the best we could before the poor Steadicam operator went numb from the waist down. (Every single shot for two days was a Steadicam shot. Every. Single. Shot.)

In this case the ambient light was established by erecting a couple of 12x12 gryffs in front of the windows on one side of the restaurant and bouncing PARs off them to recreate the daylight look. After that it became fairly simple to wheel around some Kino Flo Image 80’s to quickly shape whatever area we were shooting in. In this case we propped an Image 80, with 216 on it, on a table in front of our actress and started rolling. She looked great; the laptop looked hot but it wasn’t horrible, and my hope was that the viewer would be more interested in her than the laptop.

These stills are a little deceptive because the laptop looks better here than it does on DVCProHD, but take my word for it—the brightness competes a bit with the actress’s face. Not a lot, but enough that I wanted to try to focus a little more attention on her.

Colorista’s controls are very simple: you pick a vignette shape (ellipse or rectangle), place a top point and bottom point, set a width using a slider, feather, and done. You can see the vignette as a shape alone or as a red mask on top of your footage. Tracking is done in the usual way in Final Cut Pro, by plotting key frames on a timeline. (I have After Effects but haven’t learned it yet. Who has time???)

I’m going to go through all of this Zune footage and look for opportunities to focus attention by darkening corners and edges. I used to have this done to film all the time but I’ve yet to get any of my HD footage in front of a professional colorist. I’ve got great DIT’s who paint my cameras phenomenally well, but being able to dodge-and-burn HD images after the fact is a wonderful, wonderful thing. It will only ever end up being seen on my reel… but that’s where it counts.

(I’m in the process of reading “The Art and Technique of Digital Color Correction,” by Steve Hullfish. It’s a great primer on the art and craft of coloring. Highly recommended.)

RED Highlight Clipping: Solved?

New from RED: how to correct those bothersome clipped highlights I’ve been freaking out about for the last few days. Currently the procedure only seems to work in RED Alert using the DRX slider. This process is intended to work within REDCine using the “highlight” function but at the moment neither Adam Wilt nor I can get it to work (Intel Mac, build 90). That’s being looked into right now.

DRX works to reconstruct highlights in a clipped channel using information from the other channels. It then blends the reconstructed pixels and the original pixels together to create the most natural-looking effect.

When shooting, try not to clip more than one color channel at a time if you can avoid it. One channel isn’t hard to reconstruct. Two make it more difficult. It’s pointed out to me that two channels will rarely clip at the same time, so for part of the image only one channel will be repaired, and in other parts of the image two will be repaired (although the quality may suffer when two channels are clipped).

In RED Alert, open the R3D of the shot in question and look at the histogram. If you’ve got at least one channel that isn’t clipping, you’re in reasonable shape. If you have two channels that aren’t clipping, even better.

Using the exposure slider, back the exposure down until the curves are just touching the right side of the histogram. Then dial in the DRX slider until things look right. Make sure the matrix is turned ON with your desired white balance in place before using DRX, otherwise the algorithm won’t know what white balance you want and won’t know how to reconstruct the channel(s).

That’s it. It’s that easy. The hard part will be keeping an eye on the camera histogram when shooting to protect the quality of the highlights. It’s a strange new world, this land of RAW, and waveform and vectorscopes aren’t the only tools with which we need be familiar. The histogram is our new best friend, as that will be what tells us the quality of the data we are capturing.

A huge “thank you” to Graeme Nattress of RED for his help in solving this issue. I hope we’ll be able to bring you more info on this subject, and others, soon.

RED ONE Build 14 Latitude Tests

My goal was to see if RED’s 5000k chip is limited in exposure latitude under tungsten lighting conditions due to a tendency for the red channel to clip early. This seems to be the case, but I’m told there’s a post fix for this problem that I hope to learn about in the near future.

Here’s what I did:

-Shot a Kodak 18% gray card, with some texture to it, at different exposures to see where the camera clipped and to see where significant underexposure noise occurred.

-Shot two tests, one under tungsten light and one under tungsten + full CTB, to see how the camera did under both kinds of light.

-Originally set exposure by setting gray at 50 units using the camera’s Rec 709 output, which turned out to be a stop slower than REDLog would have me believe. Zone 4 on Rec 709 turned out to be Zone 5 in REDLog. (The ASA appears to be a true 320.)

-Took the darkest three tones for each lighting situation and boosted them to 18% gray value to better see noise; also isolated each color channel to see where the noise was coming from.

-Included histograms for each clip from Red Alert.

-Captured in RedCode28, 4K 2:1, 23.98 fps and 1/48 shutter.

I wasn’t able to check underexposure latitude as far down as I wanted because of the ambient light in the test location.

The process was: open .R3D in Red Alert and export clip; then reset white balance to 5600k and capture the histogram to see what the daylight-balanced chip was doing in each situation. The clip was scaled and output as a ProRes HQ Quicktime, 1280x720, and assembled on a ProRes HQ timeline in Final Cut Pro 2. It was then output via Compressor using H.264 VBR encoding at 1k/sec. bit rate, where I tried to keep the file size down without letting the noise get lost or exaggerated by the compression process.

Enjoy!

It’s All Up to Me Now

My quest for digital truth took me to a little known corner of the world, a private spot where there are three mountains known as The Gains. The middle one, Green Gain, is considered the most stable, and that was where I sought the Guru of all Digital Media.

After a long hike through windy prairies and along steep cliffs I found myself at his abode. At the annointed hour I let myself in and took a seat on the floor opposite the guru’s prayer matte. And then I waited.

An hour later, after discovering that Zen Monthly was simply a magazine designed to help you fill the moments of your life (2,505,600 ideas just for February alone), and realizing that the centerfold model of New Solipsist was actually the editor, I was startled by a voice.

“Sorry I’m late. Take my advice, never buy a British car.”

I half jumped out of my skin. “Where did you come from?”

The Guru pointed to his green robes. “They key very nicely, even in reality. Sorry to sneak up on you like that.” He took his seat across from me. “Tell me, son, what brings you to my retreat.”

I steeled myself, thinking of all the trouble and turmoil that brought me to this point. “It’s very simple,” I said. “I’ve been trying to wrap my mind around this whole ‘RED’ thing and it’s really perplexing. For a long time we’ve all been looking forward to an affordable, raw 4k camera for the masses, and now that we have it… I don’t think we know what to do with it. For myself, I’m learning that there’s an incredible amount that goes into making a digital camera work—and if I’m to make the RED work for me I have to learn how to do in post what other cameras have been doing for me automatically all along.”

The Great Teacher looked sedate, eyes closed, a faint smile on his lips. After a few moments he started. “Ah, sorry about that. Miles away. I do love the Bahamas.”

He leaned closer to me, as if trying to determine whether I could handle the Great Truth he was about to unleash upon me. “Tell me more about these troubles you so desperately wished for.”

“Well, I thought I wanted a camera without any processing built-in,” I whined. “But now I’m learning about all the things that cameras do for me every day that I took for granted. For example, color clipping. I’ve learned that the RED creates these interesting cyan highlights if you shoot under tungsten light, with the RED’s daylight-balanced chip, if you clip the red channel—something that’s easier to do under tungsten light because of the large red component of the spectrum. Apparently it’s not terribly hard to fix and I’m talking with RED about how to accomplish that, after which I hope to publish the solution as a tip on my blog (see ‘Self-Promotion 101,’ New Solipsist, February 2008). But I never knew that this was a common problem solved by the knee circuits in all the other cameras that I use. I know I wished for a raw camera, but now I’m discovering that someone has to take care of all these problems later, and supposedly they can do it better than it can be done in camera—but I’m not sure who that’s going to be. No one knows who will be converting the footage into dailies: is that the rental house that furnished the camera, a post house, an editor who fancies himself a colorist? Will someone do a final color correction pass or will dailies be it? There are so many questions.”

“Ah, grasshopper.” The Guru smiled, seeing a grasshopper nearby. “Now you know why you must be careful what you wish for. Yes, having a camera that dumps a pile of steaming raw data onto your plate, for you to do with what you will, seems attractive at first. THEN you find out how much has been done for you all along without your ever knowing it was happening, and suddenly there’s a new learning curve: it’s not about delivering a pretty picture anymore, it’s delivering footage and making sure someone else turns it into the pretty picture you intended it to be.

“It’s very similar to the problems my old friend, the Film Guru, used to hear all the time. His followers eventually figured it all out, and so will you. I see him less and less these days. I think he’s getting ready to retire. I guess all his silver reclamation schemes paid off.”

The Guru of All Digital Media stood, adjusted his robes, and smiled. “Let me know how things go with RED. I like them, after a fashion. It’ll be interesting to see what evolves.

“Now, if you’ll excuse me, I’m late for a meeting with Sony. I’m trying to talk them out of another prism camera and I’m already overdue. You know, for a guy who’s always supposed to ‘be here now’, I’m always late!”

He slowly started to fade away, his green robe disappearing against the background of reality. “Be careful what you wish for, young man,” he said. “Take my advice and skip the Monkey’s Paw concession on your way out.”

And he was gone.

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