Stunning Good Looks

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!

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.

Rolling_Green_Bars500.mov

I was shooting some exposure tests with a RED and I turned my tungsten reference light off to look at something on the camera. I noticed green roll bars crawling up the monitor, and quickly figured out that it was the rolling shutter interacting with the overhead cool white Ace Hardware fluorescents in the shop. The problem was completely eliminated by going to 1/40th/sec. on the camera shutter at 23.98 fps.

This was build 14. I understand build 15 will introduce shutter angle control in degrees, so it’s probably good to know that the equivalent to 1/40th is 217 degrees.

1/48th at 24 fps is right on the edge of the 60hz flicker-free window, so I habitually shoot with other cameras at 1/40th or 217 degrees just to avoid flicker issues with house power or odd discharge lights in the background. It looks to me like this practice might be mandatory with this camera. Any additional motion blur is minimal.

Notice how green the image is. Most other cameras (three chip CCD’s) don’t see the green spike in the average uncorrected hardware store fluorescent fixture. This camera sees it almost as strongly as film would. Very interesting.

The other day I found Harry, the Civil Toaster ("civil" not as in kind, but because he was in the civil service) in the driveway tossing corn chips.

“Harry… dare I ask what you’re doing?”

“It’s very simple, white bread,” he said. (Are toasters naturally rude, or is it something they develop over time?) “I read that CMOS chips have a rolling shudder, so I’m trying to find one by rolling chips and seeing if I can induce a seizure. If a chip starts shuddering, I’m halfway toward making my own camera!”

“Harry, you’re smart for a toaster. Which means if you heat up when you’re plugged in you’re already at the median for toaster intelligence, so I’m not saying much.

“What I think you’re talking about is that CMOS chips have a rolling shutter. CCD chips generally grab data in one fell swoop, after which the data is read out of the chip, the chip is blanked, and it’s then ready for another exposure.

“CMOS chips expose one horizontal line at a time, from the top of the frame to the bottom, and while they do it very quickly it’s not unusual to see artifacts from this type of scanning. Generally this shows up as slanted verticals when a camera is panned quickly. That’s because a vertical line will appear to be in one spot when the scan starts at the top of the frame, but will appear in different spots as the camera continues to pan and the shutter moves down and exposes successive lines.

“They can also be a bit noisy. CMOS sensors tend to have a lot of blue noise in the shadows.”

“Huh,” said Harry, taking his bag of chips into the shadow of the garage and looking for any that exhibit blue speckles. “So why use CMOS chips, then?”

“Well, they tend to require less power than CCD chips do. The Sony EX1, for example, would run extremely hot if it used CCD chips instead of CMOS. It deals with noise by putting the analog-to-digital (A/D) converter, which converts the chip’s analog signals to digital, right on the chip. Traditionally the A/D converter is separate from the chip and connected by wires, which can act like antennas and pick up transient signals from inside the camera and make the noise problem worse. By putting the A/D converter right on the chip the noise floor is reduced dramatically. There are solutions developing for these issues, and I’m sure we’ll see huge advancements in the near future.”

“I’m going to beat them all,” said Harry. “All I need to do is find a corn chip with low noise on the floor and I’ll be way ahead of the game.” And so he set out to find a quiet chip, snapping them one at a time while laying in the shade of the garage door.

“By the way,” he said, “from now on I’m changing my name. I’m going to be Harry the Video Toaster. Once I build my camera I’ll be famous, and everyone will shiver and quake at my name! I’m even considering joining the ‘League of Unlikely Media Superheroes.’***”

“Harry,” I said, shaking my head, “you’re twenty years too late. The original Video Toaster has long gone”

Harry looked me straight in the eye: “The Toaster will rise again!” I couldn’t tell if he was serious or if I was the victim of what he calls his “rye humor.”

***Foreshadowing alert. The reader is informed that this will pay off in time.

Life isn’t easy when one lives with overly intelligent appliances. In my case, my home is “enriched” by Harry the Civil Toaster ("civil" not as in kind, but because he used to be in civil service), an appliance who frequently makes life more interesting than it needs to be.

Yesterday I got home from work to find a pile of potato chips in the middle of the kitchen floor, and Harry in the middle sorting through them one at a time.

“What the heck, Harry!” I said. “What are you doing now?”

“Keep your crust on,” he replied. “I’m in the midst of a great scientific experiment. I read that the RED ONE’s chip is daylight balanced, and I figure if I can find a daylight balanced chip I can probably make my own camera and sell it cheaper!

“Problem is, I don’t know what a daylight balanced chip looks like. I found one that was really, really dark, and my suspicion is that it’s only good for infra-red. I want to start with a full spectrum chip before I get into the esoteric stuff.” He bit into a chip. “Maybe I’m going down the wrong track. Would a daylight chip be corn-based?”

Harry is a highly intelligent toaster. That’s not saying much; any toaster that doesn’t burn Wonder Bread is considered to have an above-average IQ.

“Harry, a chip is a silicon wafer that’s sensitive to light. That’s it. It’s not made of potato or corn. It’s basically melted sand.

“And you can’t tell if a chip is daylight balanced just by looking at it. Most chips are probably balanced for 3200k, as we add an 85 filter when we go outside. What that means is that under 3200k light the chip response in all three color channels (red, green and blue) is relatively equal, resulting in a combination of colors that’s very easy to ‘balance’ so that colors render properly. When shooting under daylight conditions an 85 filter is added because daylight is bluer than tungsten light--and without removing some of that blue, the blue channel will clip long before the other channels do, making it very difficult to white balance.”

“So you’re saying I should be looking for a tungsten chip?” asked Harry, testing another chip. “This one is really salty but it could be hiding a slight metallic taste...”

“Harry,” I said, “you should stick to sourdough. You’re out of your league. You can’t tell what light a chip is optimized for just by taste!”

“Ah, so you’ve tried?”

“No, but...”

“Just keep jabbering, butter boy.” Harry opened a bag of dip chips and dumped them on the floor. “Maybe the ruffles, with their greater surface area, will give me greater sensitivity and resolution.”

I don’t know why I bother, but I do. “Look,” I told him, “I’m not totally sure it makes a difference. There are cameras that can handle daylight situations without an 85 filter. The Sony DXC-D50, for example, has an “electronic” 85 filter that you can turn on for exteriors, but I suspect all it’s doing is reducing the blue gain to bring it in line with the others.

“That seems like a reasonable trick if you can pull it off, but it worries me. My gut says I’ll get better results using an 85 filter, so that’s what I try to do. Fortunately most of the cameras I use have 85 filters built in.”

“Yeah, and luckily they’re all smarter than you are,” said Harry. “Hey, this chip is pretty big. Does that mean it’s higher resolution? I could make a 65mm version of the RED and clean up!’

“You will be cleaning up,” I said, looking at Harry’s chip plant situated on my floor, “but not by selling cameras. And the interesting thing about the RED is that I’m told it’s a 5000k chip. I’m not sure what that means yet.”

“I think it means that it’s manly enough to kick your ass, white bread.” Harry can be very rude sometimes. “Who cares how a chip is balanced anyway? None of these balance very well at all.” He showed me by putting a chip on one finger and trying to balance it. “At best it’s a pale yellow balance, except for the dark ones. Did I say that I think those are infra-red?”

“Yes, you did. The issue with a 5000k chip is that it’s going to get used under tungsten light a lot, which means that the red channel is going to be more saturated than the others. Potentially it will clip sooner than the other channels, and if it does it will severely limit exposure latitude under tungsten light.

“Normally this would be compensated for by reducing the red gain… but the RED is a ‘raw’ camera, and doesn’t have any gain controls. It also doesn’t have a knee circuit to smooth out and desaturate highlights.

“I don’t know this for a fact, but I’m going to test it soon. I’ve already played with someone else’s footage and I’ve noticed that flesh tones do tend to clip sooner than I expect under tungsten light. I can solve the problem by desaturating the image in REDCine, but I don’t always want to be stuck doing that for most tungsten situations.

“It’ll be an interesting test. I’m also curious if I’ll run into problems in the other direction, for example if I shoot a test under skylight at 8000-10,000k. Will the blue clip sooner than the other colors?”

“Beats me,” said Harry. “Maybe a single chip isn’t the answer. Maybe I need an array of three chips. Small chips, like Fritos. Yeah, that’s it. I’m going to the store to get some corn chips.”

“Okay, Harry, and while you’re at it get some bean dip. You’re going to need an A/D converter.”

Harry stopped at the door. “Hey, you’re not so stupid after all, white bread. Maybe I’ll get some guacamole, too. After all, most of the luminance info comes from the green channel… hmmm.”

He spent most of the next hour trying to get his jacket on. Even the simplest task is difficult for a toaster. No opposable thumbs.

Today I had an interesting conversation about bit depth with my toaster.

“So, tell me,” said Harold the Civil Toaster (not civil as in kind, but because he spent some time in civil service), “why the color palette of Project Runway looks familiar without my being able to place where I’ve seen it before.”

Naturally, my jaw dropped in surprise. My toaster almost never asks me cinematography-related questions. Mostly he just complains about life and politics. He’s a crusty old fellow.

“I thought the same thing. The colors looked familiar, but also not--almost as if they were too thin or something.”

“Exactly,” said Harry. (He’s very informal as appliances go.) “The colors have the subtlety that I’m used to seeing in footage shot on Panasonic cameras, like the SDX-900 or the Varicam, with accurate secondary colors--something that’s hard for most video cameras to do, although Panasonic does it quite well.”

“I worked with a sound person the other day who’d done some time on Project Runway.” I took a tray of real butter out of the refrigerator. Harry frowns on margarines and all fats that are solid at room temperature. “He confirmed that the show was shot on SDX-900’s, but at 25 megabits per second (DVCPro25) instead of 50 megabits (DVCPro50). I think it’s safe to say that a lot of the information that’s not being recorded in DVCPro25 is color information.”

“That’s strange for a fashion show, isn’t it? You’d think they’d want to emphasize the colors more.” As toasters go, Harry is more thoughtful than most. “Is it really just about economics?”

“I s’pose. You get twice as much tape time, but yes--the colors drop off dramatically. DVCPro25 is essentially the same as DVCAM, and neither of us like how that reproduces colors.”

“I can’t tell the difference between wheat and rye on DVCAM,” said Harry. “I suppose that’s okay if you’re shooting sports, but it would be a sad choice if you’re shooting a cooking show.”

“I think they do the same thing on Top Chef. They use the right cameras but at the wrong setting. It allows them to shoot for longer periods of time, but the image could be a lot richer.” I really love the way Panasonic cameras handle color. In DVCPro50 or DVCProHD formats the color depth is complex enough to resemble film, although it’s not deep enough to create as much separation as one would see with film. My experience is that color film is much easier to light as the subtlety of color and shading helps separate subjects from backgrounds without a lot of effort. 8-bit HD and video require a lot more backlight and edgelight to pop objects away from backgrounds; even in HD it’s very easy for scenes to turn to mush if there’s not enough done to separate objects from planes.

Uncompressed and higher bit depth formats show less of this “mush” effect. The Thomson Viper, for example, reacts very much the way film does, thanks to its ability to capture a much wider range of color and tonality--although if one were recording the footage to HDCAM or DVCProHD (both 8-bit formats) instead of HDCAM SR that mushiness would quickly return.

I find that the SDX-900 and Varicam, right out of the box, are a little too subtle for my taste. I do like desaturated images if there’s enough color depth to support them, but neither of those cameras look good when the color saturation is reduced. People tend to look dead, which is great for zombie flicks but not spots or corporate projects. (Well… it’s appropriate for -some- corporate. The dead flesh tone occasionally matches the liveliness of the content.) My tendency is to go into both the color correction menus (primaries and secondaries, also known as “Color Correction 1” and “Color Correction 2"), and turn the saturation for each color up to +20. Unlike Sony, whose steps tend to be very dramatic, +20 is only a slight change and adds just a little more chromaticity. If I’m not working with a paintbox I’ll also go into the white balance preset (I believe it’s found under the Operations menu) and change it from 3200k to 3300k, just to add a tiny bit of warmth.

I’ve had great luck creating a “bleach bypass” look with the Sony F900, reducing the saturation by dialing -50 into all the colors in the multi-matrix and using a black net behind the lens. Sony colors pop quite a lot, which makes it easy to dial them back for a more subdued look. The additional resolution of the 1080 image makes color separation slightly less important. 480p and 720p Panasonic cameras fall apart very quickly when desaturated or diffused, but the palette is so soft and lovely that I never find the need to do either of those things.

“I guess money trumps quality, at least when it comes to that last 20% of quality that we’re always trying to sneak into our art,” said Harry. “Speaking of which...”

From the thick toast slot he ejects a single piece of sourdough, wearing a small tuxedo with a lavender bow tie and spats.

“What the hell is that?

“If you have to know,” Harry says smugly, “He’s the Toast of the Town.”

I’m no slave to fashion. I ate him.