In this article I wrote about classical key light placement and classical portraiture to illustrate how artists and cinematographers have traditionally gone about lighting faces. Fill light is often derided as the light that simply opens up the shadows, but it can do much more than that. It can have a shape and beauty all its own, and it can save you when your key light placement is not optimal.
The fill light can be the most important light that you place on a set, and there are a lot of choices to be made when selecting a strategy. Fill lights can be hard, soft, very soft, or soft to the point of being invisible. They can be placed on the opposite of the camera from the key or on the same side, above or below the lens, behind the camera or in front of it. Conrad Hall, ASC spoke on occasion about creating "room tone," or defining the ambience of a location with one carefully placed bounced or diffused source. This article won't go to that kind of detail but I do want to show you the power that the fill light has over a human face.
Just for fun I thought I'd put our virtual stand-in right up against a wall, which is one of the worst scenarios for lighting. My experience is that poorly placed fill shadows will give away that a scene is "lit" long before anything else will. When I'm stuck lighting people against walls or shooting in rooms with white walls I pay a lot of attention to the quality and number of shadows as they tend to become very prominent.
Here's the classic "key + fill" scenario:
The key has been slightly softened, probably by the equivalent of a 2'x3' frame of Lee 250 in front of a light that's about 6' away from the subject. The fill shadow has about the same hardness to it. This is the "45-degree-off-lens-axis-and-tilted-45-degrees-down" formula that every film school teaches. This probably stems from the good old days of big studio features where all the lights were hung from an overhead grid. From this angle the key works well on many faces (with a little tweaking: perhaps more frontal for women and more from the side for men) and the fill does a fair job of filling in the shadows.
There are some drawbacks to this strategy. There are a lot of situations where the additional fill shadow says "lit" to me. In nature it's rare to have a hard fill shadow that's opposite the main light shadow, and unless the fill is at least a little bit hidden by increasing the size of the source and softening the shadow it can be a bit of a lighting giveaway. Still, there's an awful lot of projects that are lit with some variation of this lighting setup. I see it a lot in episodic television: when I look into an actor's eyes I can see two sources, one on either side of the camera. It can look quite good if done correctly.
For me "correctly" means the fill source is very large and very soft, so that the shadows it casts on walls and furniture have indistinct edges and are very delicate, and not distracting. There are limited times when a fill source can be hard; the most obvious is if I'm filling someone that is quite far away from the camera and the hard shadow isn't obvious due to diminished perspective or soft focus.
The key drawback of this key+fill setup is that there are only two tones on the face: the brighter tone on the key side and the darker tone on the fill side. A soft key creates greater tonal distribution across the face but a fill light placed at this angle will only contribute one tone on the shadow side.
Some faces have jawlines that cause both the key and the fill lights to merge into one dark shadow beneath the chin. This can also be a bit of a lighting giveaway. One distinct shadow is generally more pleasing. There are exceptions to this, though, and we'll get to one of those later on.
Occasionally this lighting setup will leave dark spots in the crevices around an actor's eyes, particularly where the corner of the eye meets the bridge of the nose. This is particularly obvious on the key side, because the brightness of the key makes adjacent shadows look darker than they should.
For the next setup we're going to bring the fill light in line with the lens height, but still 45 degrees opposite the key:
This setup works a bit better for digging into eye sockets and eliminating double shadows under chins. The fill light is still offset 45 degrees from the lens axis so it's not getting into all the corners that it could. For example, in this image it is illuminating the corner where the camera right eye meets the bridge of the nose but this is the exception to the rule. Fill lights that are offset from the camera will often not reach into this crevice, and the result is that the darkest part of the face--where neither the key nor fill light reach--is juxtaposed against the brightest part of the face--the key side--which makes it appear darker.
This next image shows what happens if we soften the fill light considerably:
The previous image showed what would happen if we used a light through a 2'x3' frame of Lee 250 6' from the subject. This shows what happens if we make that source a 6'x6' frame of grid cloth, which is much denser than Lee 250. By making the source bigger, and by eliminating the beam of the light and making the dense diffusion do all the work (the glowing diffusion becomes the sole light source), we can make the shadow very soft indeed.
Let's move the light lower:
This shows the fill light still offset 45-degrees from the camera but placed low and tilted up at 45 degrees instead of high and tilted down. I don't see this very much anymore. This technique is seen most often in black-and-white movies made in the 1940s, back in the days when stars had to look good at any cost and shadows be damned. I wondered for far too long why this position was so popular at that time and eventually realized it was simply opposite in angle to the key light. One was high and pointing down, the other was low and pointing up from the opposite side of the camera.
In old movies this fill shadow is very hard, much harder than I show here, although it is faint because it is not the only fill light. In those movies the set has an overall fill light, and this additional light is meant only for the actor. It's left as a hard source because it doubles as an eye light, and eye lights pop more if they are hard points of light, or specular highlights.
A specular highlight emits all the light energy from one point, the filament, so that one point is very bright. A soft source may emit the same amount of energy but over a wider area, so while the light coming from the soft source may be the same in total every part of the diffusion or bounce card is radiating less light. A big source means a bigger highlight in the eye, but one that's dimmer overall because the light energy is so spread out over the source's surface.
Here's what happens if we diffuse the fill light further:
As a regular fill position I think this is too obvious for modern use because, while the fill is very soft, any hand gestures near the face will cause an obvious shadow from both the key and the fill as well as a wall shadow that's 180 degrees off from the key. Shadows that fall directly opposite each other often look fake.
In film school we're taught that lighting from under the lens denotes horror, but that's if the light is hard and looking almost straight up at a face. Light from below the lens can be quite beautiful.
Here the fill light is directly below the lens. I show an example of this technique in this article. Very soft fill light from below the lens can be gorgeous. When I was a camera assistant I worked with a DP who both keyed and filled with bounce light off 4'x8' sheets of foam core placed under the lens. The light had a very soft, natural feel, as if sunlight through a window reflected off the floor onto the actor's face.
There's a great example of soft light from below in the film Driving Miss Daisy. There are several sequences where the camera just wanders through Miss Daisy's house, and all the rooms on one side of the hallway are lit with soft, warm, upward shadows while the other side was lit with soft blue sidelight. I realized that the motivation for the lighting was warm sun striking the floor through windows on the south side of the house and blue skylight coming through windows on the north side of the house.
Let's talk more about high-angle lights on the next page...