Often, when you need to match elements to a source, the steps outlined in Chapter 5, "Color and Light: Adjusting and Matching," for matching brightness and color are sufficient. In many scenes, however, there is clearly more involved with light than brightness and color. In some cases, the direction of the light plays a role, especially where the quality of the light is hard (direct) rather than soft (diffuse). There is such a huge variety of light situations possible in a shot, and in an infinite array of combinations, that it becomes difficult to make any broad statements stand up about lighting. This section, however, tries to pin down some general guidelines for manipulating the light situation of your scene. Location and QualityYou may have specific information about the lighting conditions that existed when your plate footage was shot. On a set, you can easily enough identify the placement and type of each light; this information is contained to some extent in a camera report also. If the source shot was taken only with natural lighting, you're seeking the position of the sun relative to the camera (Figure 12.1). This information can help you puzzle out highlights and shadows when it's not clear how to match the lighting of the plate. Figure 12.1. Three shots lit only by the sun; in each case shadows tell you the light is coming from behind and to the right of camera, but as the sky becomes more overcast, the light becomes more diffuse and its direction more difficult to discern.Sometimes the location and direction of light is readily apparent, but surprisingly often, it's not. As I write this, I'm looking out the window on an overcast day. The sunlight is coming from the south (on my left), but as I look at objects in my backyard, it seems to have no direction at all, because it's not direct, it's diffuse. Furthermore it keeps changing. The quality of light in this scene is the most subjective and elusive of criteria. Hard, direct light casts clear shadows and raises contrast, and soft, diffuse light lowers contrast and casts soft shadows (if visible at all). That much seems clear enough. But these are broad stereotypes, which do not always hold as expected. For example, hard light aimed directly at a subject from the camera's point of view flattens out features, effectively decreasing contrast. And when multiple lights combine to light a subject, hard shadows can be diffused, a typical situation with artificial light (Figure 12.2). Figure 12.2. To simulate the artificial lighting of a baseball stadium at night, this scene was lit from both sides with nearly equivalent key lights, causing light and shadow areas to overlap and cancel one another out to some degree. (Image courtesy of Tim Fink Productions.)Heightening Drama with LightAlthough the color and contrast of the scene can be nailed down precisely, light direction and quality can be slippery, surprising, changeable, and difficult to re-create. All true, but there's still plenty you can re-createor get away withif you follow a few basic guidelines:
Mastering the use of light in a scene is no simple matter. For centuries, painters defined themselves as much by their observation and use of light as anything; a new school of thought would develop, typically driven by a "master" who had observed something novel and revolutionary about how light works, and the course of art history would be changed. So instead of looking for the lazy quick fix, you are encouraged as always to keep shooting reference and scouring it for details you can steal. Neutralizing Light DirectionIf your source was shot with a light direction that is incorrect for the composited shot, that's a pretty big problem, depending on how hard and directional the light actually is. The solution is generally to neutralize, rather than to try to fix the discrepancy. For the purposes of discussion, consider a situation in which shadows and highlights give a clear indication from where the light is coming. Also assume that a simple quick fix, such as flopping the shot, is not possible, which it usually isn't. In such a case, you would first look for light direction clues that you could remove from the element; for example, look for cast shadows falling on an area of the shot that can either be removed or replaced (probably via matting and rotoscoping, as in Figure 12.5). In areas of the footage that can't be removed or replaced, use the Levels control to reduce contrast, raising Output Black to neutralize shadows and Output White to knock down highlights. There will likely be unwanted side effects, so you must do your best to strike a happy medium (Figure 12.6). Figure 12.5. The most immediate indication that Sir Isaac has been lit from the left is his long cast shadow, but you have the option of including it or not when pulling the key.Figure 12.6. Removing the shadow and raising the black levels helps to eliminate at least the first impression of the strong direction of the light, even in a case as extreme as this.If adjusting the image directly to soften highlights and shadows isn't looking so good, you can get creative in adding the equivalent of a soft filter on the image. To do this
These blurred layers soften the highlights and shadows, respectively. With Screen mode, the overall levels will not change; with Add, they will brighten slightly (Figure 12.7). Figure 12.7. The effect of a soft lens filter is created with two extra duplicates of the source, each blurred and then set to Add (or Screen) and Multiply, respectively, each with an Opacity of approximately 30%.Far from being the only such adjustment you can make, this is one pretty much devised on the fly to give a specific example; different shots might well require different settings. More generally, the principle of combining an image with blurred and matted versions of itself can be a highly effective way to change not only its lighting qualities but also its overall look. Leveling Uneven Light and HotspotsThere is a simple trick that you can use to even out the lighting in cases where it should appear uniform. The basic idea is simple: Create a counter gradient and use it to weight to your image adjustment by bringing up the shadows, bringing down the highlights, or both. What's surprising is how powerful the technique isand to how many situations it applies. You can create the gradient to do this by eye. In some cases, such as scenes with low contrast, you can use the inverted, blurred source itself to create the matte. But as a compositor used to looking at light, you should be able to discern where the hotspot is, and how far it reaches (Figure 12.8). You might even find this kind of fun. Figure 12.8. This scene is lit by a single key light aimed at the center of the scene, causing a distracting hotspot on the torso of the second bunny from the left.The next step is to create a white-to-black gradient using the Ramp effect that matches your perception of the hotspot in the scene (Figure 12.9). You could apply the result directly to the scene with a blending mode, but you'll have more control if you apply it as a luma track matte to an adjustment layer containing a Levels or Curves effect. This allows you to select whether you're adjusting highlights and shadows or gamma. Figure 12.9. A simple gradient created to match the offensive area of the hotspot. The center and edge of the radial gradient, created with the Ramp effect, have been positioned by eye to match Figure 12.8.The result won't necessarily obliterate all evidence that there was hot lighting in some area of your scene (Figure 12.10), but as always, the goal is not only aesthetic beauty but also the viewer's focus. If there seems to be a distracting spotlight on the middle of some part of the scene, there's a problem. The same technique can even help when you're attempting to pull a key from an unevenly lit set, although tools such as Keylight already compensate for these types of image defects. Should the camera move during the shot, you can even consider marrying the gradient start and end points to a tracker with an offset, either via expressions or parenting. (See Chapter 8, "Effective Motion Tracking," for more on this.) Figure 12.10. It's not as though all traces of the single hard key light have been eliminated, but that was not the aim of this adjustment. Instead, the effect of the light has been reduced so that it no longer puts the viewer's focus in the wrong place.Conversely, you can also create a lighting effect this way; a radial gradient at the center of the frame, with the corners slipping away to darkness, creates a vignette or eye light effect, often associated with projected or heavily treated film and with handheld low-light shooting. The easiest way to do this is not with Ramp but with a heavily feathered and inverted elliptical mask applied to a black solid (Figure 12.11). Figure 12.11. Reference of film footage that was shot and processed with a vignette, and addition of the equivalent vignette effect in After Effects, by double-clicking the Elliptical Mask tool to fill the frame, then opening the mask controls (MM), checking Invert, and setting a very high Mask Feather (500 for this 2 K resolution source) and Mask Expansion (50 pixels).
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