The best compositing book just got 7er

Mark Christiansen has updated his excellent book for AE7. It now features many more sample projects, including some HD footage provided by Pixel Corps. Still the same great focus on hardcore compositing, and still the same space-filling chapter at the end by some Stu guy.

Adobe After Effects 7.0 Studio Techniques

Linear Color Workflow in AE7, Part 6

Extracting Linear HDR (AKA scene-referred values) From Camera RAW files. Wee!

Much is made of the overexposure latitude contained within RAW images created by higher-end digital cameras such as DSLRs. The truth is, there can be extra data up there, but it may be hard to artfully extract. For the same reason we put the magenta filter on the Viper, the over-range values in a RAW file may be monochromatic and otherwise discontinuous from those in the sweet spot of the chip's sensitivity.

However, Adobe Camera RAW does a mighty fine job of milking every last bit of usable picture data out of a RAW file, and it is now included with After Effects 7.0. If you underexpose your RAW shots enough so that the highlights aren't clipping, you can effectively create single-exposure HDR images for use in your 32bpc projects.*

First, set up your project for a linear floating point workflow. This means switching the bit depth to 32bpc and selecting a linear (gamma 1.0) profile as your Project Working Space.

Then import your RAW file. Here's what one .NEF from my Nikon D70 looks like in the Camera RAW window:

Notice that the clouds are almost clipping, but Camera RAW is rounding into the clip nicely. That's lovely for photography, but for visual effects I'd like to get a more accurate representation of the actual light values present in the scene. I need to remove all the artful tweakings of the tone curve that Camera RAW has suggested.

To do this, set Shadows, Brightness, Contrast and Saturation all to zero. Then go into the Curve tab and select the Linear preset for the curve.

Feel free to adjust other settings to taste, such as those found in the Detail and Lens tabs. Remember, there is always subjective processing involved when making a viewable image from a RAW file, so don't shy away from these controls. You should also select a White Balance setting that makes your image look the most neutral (if you want it to have a color cast, better to do that later in float).

Your final step is to adjust the Exposure slider until no highlights are clipping. Use the histogram and the Highlights checkbox in the upper right to guide you. Find a setting just below the point at which you begin to clip.

Here's what my image looks like after following these steps:

Now hit OK (twice) and you are returned to After Effects. Select the footage item in the Project pane and you'll see that the profile it is importing via appears next to the thumbnail. Since our Project Working Space doesn't match any of the four export profiles supported by Camera RAW, our image defaults to the sRGB space. Which means that once we add it to a comp, it requires the same conversion to our project's working profile as any sRGB image would — the same one we went over in Part 1:

Now that we've got a comp that contains our linear and underexposed scene-referred pixels, we can simply add an exposure effect and boost it up until our image "looks right." In doing so, we'll push the brighter pixels into the overbright range, effectively creating an HDR image. Here's my image exposed up by a stop:

Photographers may be distressed by the clipped clouds in this image. Speaking for myself, when I shoot stills, I'm trying to artfully compress the broad dynamic range of the world into a viewable range. In other words, I'm trying to take a High Dynamic Range world and squeeze it onto a Low Dynamic Range print. But what we just did is the opposite — we took a LDR image and made it HDR. Why do such a thing? Images that visual effects artists shoot are often used not as standalone works of art but as ingredients in a final composite. Our HDR sky, blown out as it may appear, will react very realistically to subsequent compositing. If we blur it or composite transparent things in front of it, we will see the detail in those clouds come back in a photographic way.

Or we can play with other ways besides just tone curves to create a more pleasing final image. For example, we could take an image like this:

...and multiply it over our shot, for this result:

Happy RAW shooting!

* In other words, it's more your RAW format's ability to handle underexposure than overexposure that allows it to capture HDR imagery!

fxguide podcast

It's up! If you can't get enough of this linear stuff, check out my interview (download .mp3 link) on fxguide's awesome podcast. There's a great article that sums it up nicely as well.

I've also allowed fxguide to mirror my linear-light in AE7 workflow articles in hopes that they reach more people. ProLost is still the place to get the latest and greatest ramblings though.

Thanks very much to John Montgomery and everyone at fxguide for having me on the show. I've mentioned before that I'm a huge fan of the podcast (iTunes link), and it's an honor to be a part of it.

Maybe with all this I can finally shut up about this linear crap for a while!

A Tale of Three Blurs

There are three Blur effects in After Effects that are commonly used, have been upgraded to 32 bpc floating-point color for version 7, and are generally misunderstood.

Gaussian Blur

Gaussian Blur has the simplest UI of the three — “Blurriness” and options for blurring in X, Y or both. Historically, Gaussian Blur was known as the premium blur for those who could afford its increased render times. While this was once true, it is now purely a myth. Gaussian Blur uses the exact same blur engine as

Fast Blur

…except that Fast Blur adds a very important “Repeat Edge Pixels” option. So for the record, there is no advantage in using Gassian Blur over Fast Blur. Gaussian Blur is obsolete.

Box Blur

Box blur is like a Volvo. It’s boxy, but good. Oddly, it’s best feature is that it can, if desired, be less boxy than the other two.

Box Blur is the simplest kind of blur, and at its defaults produces “squarish” results. However, it features an Iterations slider that allows you to perform this box blur operation any number of times you would like. At three iterations, Box Blur is identical in quality to Fast Blur. At four or five, it is better, producing a softer, rounder blur. When blurring small, bright floating-point things, you may be glad for this extra quality.

Or you may find that at one iteration, Box Blur’s simple blur is a handy utility. For example, used in Horizontal or Vertical mode, Box Blur is a better approximation of motion blur than is Directional Blur. Photographic motion blur should have that squared-off look, not a Gaussian-esque smoothness.

The only bummer is that Box Blur’s main slider works differently than Fast Blur’s, so if you need to “upgrade” to Box Blur you’ll have to eyeball your values to match.

Since Box Blur does everything the other blurs do and more, I often reach for it first, usually setting Iterations to three or four by default.

So just like Carson Kressley’s rule of suit jacket buttons (middle, top, bottom = always, sometimes, never): 

• Box Blur = Always
• Fast Blur = Sometimes
• Gaussian Blur = Never