Passing the Linear Torch

I used to show you weird crap like this all the time

Back in the day I blogged a lot about how compositing and rendering computer graphics in “linear light.” a color space in which pixel values equate to light intensities, can produce more realistic results, cure some artifacts, and eliminate the need for clever hacks to emulate natural phenomena. Along with Brendan Bolles, who worked with me at The Orphanage at the time, I created eLin, a system of plug-ins that allowed linear-light compositing in Adobe After Effects 6 (at the mild expense of your sanity). I also created macros for using the eLin color model in Shake and Fusion. Along the way I evangelized an end to the use of the term linear to describe images with a baked-in gamma correction.

Then Adobe released After Effects 7.0, which for the first time featured a 32-bit floating point mode, along with the beginnings of ICC color management, which could be used to semi-automate a linear-light workflow. The process was not exactly self-explanatory though, so I wrote a series of articles (1, 2, 3, 4, 5, 6) on how one might go about it.

Then I rambled endlessly on fxguide about this, and in the processes managed to cast a geek spell on Mike Seymour and John Montgomery, who republished my articles on their fine site with my blessing.

This week Mike interviewed Håkan “MasterZap” Andersson of Mental Images about the state of linear workflows today on that same fxguide podcast.

Which is so very awesome, because I don’t want to talk about it anymore.

It’s just no fun going around telling people “Oh, so you put one layer over another in After Effects? Yeah, you’re doing it wrong.” Or “Oh, you launched your 3D application and rendered a teapot? Yeah, you’re totally doing it wrong.”

You are doing it wrong. And I spent a good few years trying to explain why. But now I don’t have to, because Mike and MasterZap had a great conversation about it, and nailed it, and despite the nice things they said about ProLost you should listen to their chat instead of reading my crusty old posts on the subject.

Because it has gotten much, much simpler since then.

For example, there’s Nuke. Nuke makes it hard to do anything but work in linear color space. Brings a tear to my eye.

And the color management stuff in After Effects has matured to the point that its nearly usable by mortal men.

Since I’ve seen a lot of recent traffic on those crusty old posts, here’s my linear-light swan song: a super brief update on how to do it in AE CS4:

In your Project Settings, select 32 bpc mode, choose sRGB as your color space, and check the Linearize Working Space option:


When importing video footage, use the Color Management tab in Interpret Footage > Main to assign a color profile of sRGB to your footage:


Composite your brains out (not pictured).

When rendering to a video-space file, use the Color Management tab in your Output Module Settings to convert to sRGB on render:

That’s the how. For the why, well, those crusty old articles could possibly help with that, especially this one on color correction in linear float, and this one on when not to use linear color space. Part 6 is still pretty much accurate in describing how to extract a linear HDR image from a single raw file using Adobe Camera Raw importer in After Effects, and this article covers the basics fairly well, although you should ignore all the specifics about the Cineon Emulation mode, which never should have existed. This little bit of evangelism is still a good read.

But the ultimate why answer is, and has been for a while now, within the pages of a book you should have anyway: Adobe After Effects CS4 Visual Effects and Compositing Studio Techniques (deep breath). Brendan Bolles guest-authored a chapter on linear light workflow, and not only does he explain it well, he gives many visual examples. And unlike me, Mark keeps his book up-to-date, so Brendan’s evergreen concepts are linked directly to the recent innovations in After Effects’s color manglement.

OK, that’s it. Let us never speak of this again.

Update on Wednesday, September 30, 2009 at 2:09PM by Stu

I can’t believe I wrote all that without once linking to the official Adobe whitepaper on Color Managed workflows in Adobe After Effects CS4. It’s a great write-up, super detailed, and accurate in every way. Further proof that my work here is done.

Magic Bullet Mojo

One of my fxphd shots with nothing more than Mojo applied

If you watched my tutorial on achieving the “Hollywood blockbuster look” using various color correction tools, you probably noticed the consistent theme among the very different example films I showed you how to match—the ubiquitous cool shadows, warm highlights look. Whether the film is bleached of all color (like Terminator Salvation) or super saturated (Transformers: Revenge of the Fallen), and whether it is overall warm or cool, modern films have zeroed in on a color correction style that tends to preserve skin tones and set them off against a cooler backdrop.

The same shot before Mojo

It’s more than possible to achieve this look with Colorista or Magic Bullet Looks (check out the Blockbuster preset—it’s been there since day one). But sometimes you just want to spruce up your footage quickly and easily, without a hundred presets to peruse or a powerful colorist’s interface to manipulate.

Sometimes you just want to take your footage that already looks pretty darn good, and give it a little bit of… Mojo.

Magic Bullet Mojo from Red Giant Software is the pocket-sized screwdriver to Magic Bullet Looks’s cordless driver drill. It does one thing, and does it quickly and easily. It gives you that Mojo thang with just a few simple sliders to adjust, and ships with presets for popular looks.

Unlike Looks and Colorista, Mojo is a bit of a one-trick pony. It’s simple and easy and priced to be an impulse-buy at $99 US. One license allows you to use it in Final Cut Pro, Premiere Pro, Avid, After Effects, and Apple Motion [UPDATE: Now Sony Vegas as well!]. Mojo is also now a part of the Magic Bullet Suite.

Mojo has some cool new features that you’ll recognize from the tutorial video. Since it’s all about skin tones, Mojo has simple sliders for emphasizing, cleaning up, and adjusting skin coloration. It even features a helpful overlay that gives you the same kind of skin-tone guidance for which expert colorists rely on their vectorscopes.

Here are some preemptive answers to questions you might have about Mojo:

Q: Isn’t this look just a cheap gimmick? Just a trend that could pass in a few days/weeks months?

A: Maybe, but in another way it’s an evolution of practices many years old in color correction suites around the world. Is it overused? Sure, but that’s because it works. Personally, I love the way it looks, when done tastefully. We provide the tools, you provide the taste. Try turning the Mojo slider down instead of up when you first apply it.

Q: I applied Mojo but my skin tones aren’t popping.

A: Your faces might be underexposed a bit. Try reducing Mojo Balance—it’s the control that determines what’s a shadow and what’s a highlight. Skin tones tend to fall right in between.

Q: I tried the demo and Mojo makes my footage look terrible.

A: Mojo is designed to work with footage that’s pretty solid to begin with. If what you need is color correction, then reach for Colorista. If you love the way your footage looks before Mojo, try the “Mojito” preset—it’s just a little bit of Mojo.

Q: Why do the sliders have more range in FCP than in After Effects?

A: Actually, they have the same ranges, but in After Effects we can have the slider min/max be different from the absolute min/max. I wish FCP would let us do that too, because the ranges we show in AE represent a “sweet spot,” and the values outside those ranges are kind of pushing things into the red a little.

Q: I already have Magic Bullet Looks, why do I need Mojo?

A: Because you don’t open a walnut with a jackhammer. In my own experience, Magic Bullet Looks is occasionally a bit to much overhead for a quick-turnaround project. Mojo is so quick and easy that I reach for it all the time, saving Looks for those occasions when I want to invest some time into my color grading.

Q: Will you tell my clients I’m using it?

A: No. It’ll be our little secret.

The Foundry Un-Rolls Your Shutter

The Foundry have released a $500 plug-in for Nuke and After Effects that attempts to remove rolling shutter artifacting, AKA “Jell-o cam,” from CMOS footage (RED One, Canon HV40, Canon 5D Mark II, etc.). It’s based on a technology demo that they showed at NAB earlier this year.

I’ve tried it, and it works—sometimes. The Foundry are well known for being leaders in the motion estimation field, and they have harnessed their unique experience in this area to attempt the impossible: a per-pixel reconstruction of every part of the frame, where it “would have been” if the shutter had been global open-close instead of read out a line at a time.

When it works, it’s brilliant. But the more motion you have in the frame, the more likely this plug-in, mighty though it may be, will get confused. Unfortunately, when this happens, parts of the image turn to scrambled eggs.

It’s a very similar problem to re-timing 30p footage to 24p actually—in fact, I wish The Foundry had added an option for frame rate conversion to this plug-in. Although, in fairness, I would only rarely use it.

Folks are always asking me about converting 30p to 24. I responded in a thread on the Rebel Café:

…The more motion you have, the more likely it is that any optical flow re-timing system is going to encounter problems.

Not even getting into the combat shots, here’s the Apple Compressor method referenced in Philip’s tutorial failing on one of the more sedate shots in After The Subway:

Now I’m not saying that you won’t occasionally see results from 30-to-24p conversions that look good. The technology is amazing. But while it can work often, it will fail often. And that’s not a workflow. It’s finger-crossing.

On a more subtle note, I don’t think it’s acceptable that every frame of a film should be a computer’s best guess as to what happened between captured frames. The magic of filmmaking comes in part from capturing and revealing a narrow, selective slice of something resonant that happened in front of the lens. When you do these motion-interpolated frame rate conversions, you invite a clever computer algorithm to replace your artfully crafted sliver of reality with a best-guess. I feel (and feel free to disagree, I won’t bother arguing) that this artificiality accumulates to create a feeling of unphotographic plasticness. Screw that. Didn’t you select the 5D because you wanted emotionally resonant imagery? You’d be better off with a true 24p video camera that works with you rather than against you, even if it doesn’t give you the convenient crutch of shallow DOF.

To be crystal clear, that’s Apple Compresser failing to properly estimate the motion in one particular frame when trying to convert from 30p to 24p. Nothing to do with The Foundry or their new plug-in, which actually tackled that same shot quite well.

The Foundry knows that they’ve made a tool to help us limp along while camera manufacturers sort out this CMOS issue. Like any crutch, I wouldn’t plan on leaning too hard on it—but kudos to The Foundry for attacking this problem head on, and making a product out of a technology demo in record time.

Update on Thursday, August 6, 2009 at 2:28PM by Stu

Of course, there will always be some rolling-shutter artifacts that can never be fixed:

Color correcting the Stunt People short

…using the DV Rebel Tools.