The Four Attributes of Light

Lighting is one of the most challenging aspects of video production, but the right equipment and knowledge of the four main attributes of light makes great lighting possible in any scenario.

Capturing Light

Your camcorder captures light, records it and stores it in such a way that allows you to play it back so everyone can see what your camera saw. That’s all it does and, more importantly, that’s all it knows. You are responsible for controlling the light you are about to capture. Light has four attributes you can work with to make your scenes look the way you intend. The color, intensity, quality and direction of your light sources all play a role in determining the overall look of your video. Whether your goal is a contrasty film noir scene or a flat lifeless office scene, it’s your job to light it properly so your camera will capture the results you need.

COLOR – Part 1

Understanding how color and light work is essential to successful lighting. There are two factors to consider: getting colors to look natural, and using color to set the mood of a scene. Achieving natural looking colors in your footage has everything to do with the white balance you set on your camera and what’s referred to as the color temperature of the light sources in your scene.

All light sources have a color temperature, which is measured in degrees kelvin. It’s a bit confusing, but this has nothing to do with how hot a light source is to the touch. Instead, light sources with different color temperatures produce a wide range of color casts that you must counteract with your white balance.

With the right equipment and a deep knowledge of the four main attributes of light, you can achieve great lighting in just about any scenario.

Sources like a lit match or tungsten lights have lower color temperatures at or below 3200k and give a amber or reddish cast, while sources with higher color temperatures like direct sunlight or shade have color temperatures of 5600k and above and give off a more bluish cast. Our brains are extremely adept at counteracting these color casts even in mixed temperatures, so that white generally looks white, even when we walk from a low lit room to the bright outdoors. We basically have perfect auto-white balance.

Your camera, however, needs a little more help to render colors naturally. It only has the ability to interpret one color temperature at a given point in time. With your white balance set to auto, you might get away with a shot that moves from indoor tungsten lights (3200k) to outdoor sunlight (5600k), but what about mixed temperatures?

Let’s say we have an indoor interview, and we want to use the natural light coming in through the window. In our light kit, we have a couple tungsten lights. Mixing the tungsten lights (3200k) with outdoor light (5600k) streaming in through a window puts our camera in a difficult scenario.  White balancing to 3200k, or “indoor,” will result in a bluish tint on the parts of our scene receiving the outdoor light, while the parts hit by the tungsten light will look natural. Setting our balance to 5600k, or “outdoor,” will result in amber tint to the portions of the scene lit by the tungsten light. The whole idea is to make sure all your light sources have the same temperature, so your colors appear natural when you set your white balance.

Different light sources have different color temperatures, affecting the final look of the footage. When working with mixed color temperatures, it is sometimes necessary to apply colored gels to keep the scene looking natural.

Luckily, there are several techniques for dealing with this. You can use color temperature correction gels over your lights or windows to convert from them from one color temperature to another. For example, placing a CTB (color temperature blue) gel over the tungsten light in our example would convert the 3200k light into 5600k light. Now setting your white balance to 5600k, or “outdoor,” would produce natural color in your footage. This would also be useful if you were mixing the tungsten light and an LED or fluorescent light that had a 5600k temperature.

Another option is to cover your windows with CTO (color temperature orange) gels. This would convert the 5600k light to 3200k light, and setting your white balance to 3200k or “indoor” would result in natural color for your shot.

Color Part 2

Getting natural looking colors is a great place to start, but once you’ve got the white balance all set, you may want to use color to create a mood in your scene. That “white light” you see is really the additive property of light at work. Red, green and blue light are combining to create that “white.” In fact, these three primary colors combine in different variations to form every color of light that your camera sees. We can of course, filter out some color in order to give our scene the look we want using what are commonly referred to as “party gels.” Unlike color correction gels, which are used to help balance the color cast of different sources, party gels are used to intentionally introduce color into your scene. It’s an important attribute of light we can manipulate, to help sell our story.

Intensity

The intensity of a light refers to its brightness. The intensity of the source itself is measured in lumens, while footcandles or lux measures the intensity of light hitting a subject. If your light intensity is too low, you have to increase the gain or ISO of your camcorder in order to record correctly exposed video. This can increase the amount of noise in your footage. If it’s too high, you’ll have to close your iris down, increase your shutter speed or ideally, use a neutral density filter to reduce the amount of light passing through your lens.

Luckily, you can control the intensity of a light source with a few different tools. One option is to switch the wattage of your bulb. Another is placing a neutral density gel over a light or window, which will cut the intensity without affecting its color temperature. A scrim has a similar effect.  You can also use a dimmer, but be aware that this will shift the color temperature of a tungsten light. Some LED lights have built in dimmers that don’t cause this shift. Finally, you can simply adjust the distance of your light from your subject.

Combining lights with different intensities can help you control the lighting contrast ratio. The contrast ratio is the difference between the brightest and darkest portions of your scene. Much like our ability to adjust for extreme differences in color temperature, our eyes can easily adjust for extreme contrast. While we are indoors in normal room light, everything is well lit and we can make out even subtle details in the darkest parts of the room. Glancing out a window changes nothing. We can see clearly everything in direct sun while the details in the outdoor shadows are visible too. We can also see both light conditions at the same time. The indoor details and the outdoor details are clearly visible to us.

Our cameras, however, aren’t so adept. Auto-iris may be passable when we move from a dark scene with a low contrast ratio to a much brighter scene with a low contrast ratio, but when we try to capture a scene with a high contrast ratio, such as a low lit room with a bright window looking out into the daylight, our cameras often fail miserably.

Simply put, the higher the contrast ratio, the more dynamic range your camera will need to be able to capture your scene without underexposing your shadows, or overexposing your highlights. A large production crew will have meters that measure the amount of light in a scene and will carefully insure that everything falls within their camera’s dynamic range. This allows the camera to capture all of the detail in the scene to give editors flexibility to color correct and grade in post.

With a combination of increasing and decreasing the intensity of different light sources, you can easily remedy most problems you may find indoors.You can add light to the darker areas, or reduce the intensity in the brightest areas. Of course, the right amount of contrast just depends on your artistic vision.

From experience I can tell you that it can be extremely difficult, if not impossible, to match an interior setting to an exterior setting without placing neutral density gels on the windows if you are shooting from the interior and expecting to correctly expose the exterior. Conversely, if you are expecting to shoot from outdoors and correctly expose interior scenes through a window you will need enormous amounts of light inside.

Not to worry because with careful planning and preparation you can create superb results by shooting when the intensity of the outdoor lighting matches the intensity of the indoor lighting.

There is a time when the sun is close to the horizon that the outdoor lighting intensity is very closely matched to the average indoor lighting of most buildings and residences. During this time the lighting results can be spectacular but there is one caveat and that would be time. You only have about 30 to 45 minutes to shoot but like I said, careful planning can yield wonderful results.

Quality

A third critical attribute of light you can control is quality. The quality of a light source affects how the highlights and shadows look in your scene. The two common terms used to describe light quality are hard and soft.

Side by side photos of a person being harshly lit by the sun at high noon and more softly lit by using a diffuser.
Hard light, such as the sun at high noon, will create intense shadows and more contrast. Diffusing the light produces softer shadows and reduces contrast, as seen in the image on the right.

Hard light is produced by small sources and creates crisp, sharp transitions between highlights and shadows. Two good examples of a hard light source are the sun at noon, and a clear incandescent bulb.

Soft light is produced by larger sources, and produces diffused gradual transitions between highlights and shadows. Essentially, soft light will “wrap” around your subject and illuminate the shadows to a certain extent. Two examples of soft light sources are overcast skies and softboxes. Soft light is scattered, and therefore very difficult to shape and control.

If you’ve got a hard light source, you can assert some control over it. You can diffuse it with material to make it softer, use flags to shape it or use reflectors to bounce some light back into the shadows to lower the contrast ratio. Even direct sunlight on a sunny day can be rendered creatively with dramatic results.

Direction

The fourth attribute of light is direction, or angle. This is a crucial component to achieving realistic lighting.

Lighting your subject from the side can add depth and even mystery to the image, while lighting from the front will produce a flatter and more revealing image.

The direction your most intense light (commonly called the key light) comes from determines where your primary shadows will fall. In other words, if you want to mimic sunlight coming in through a window, you don’t want to place a hard light directly above your subject. You also want to consider the effect that direction has on your subject. Lighting a face from the front at eye level will create an extremely flat looking image, while light coming from the side will reveal texture and shape.

Bringing it all together

While each attribute can be described individually, the reality is that color, intensity, quality and direction give a specific light source the unique look it produces.  Combining various light sources with different properties allows you to properly light a scene in the precise way you want. You are in control of the intensity and contrast ratio, the quality of the shadows, the color that creates the mood and the direction that reveals or conceals details and mimics real world lighting. The infinite number of combinations is what makes lighting so complex, yet so powerful.  Ultimately, your camera can only capture the light you put in front of it, and the most important thing is knowing you can bend it to your will to get stellar looking images.

Sidebars

How color temperature is measured

Color temperature meters measure in units of kelvin, which is a measurement of absolute temperature and has the scientific symbol K. Physical temperature which you can feel is measured in thermal radiation. Color temperature which you can see is measured in electromagnetic radiation. The sun radiates electromagnetic energy at 5000k at noon. Most cameras and films are designed to respond favorably to 5000k. Some film (type B films) are designed to give accurate color results at 3200k. As the sun rises and sets, the temperature changes due to the effects of the earth’s atmosphere. Standard incandescent 100 watt bulbs radiate at about 3200k.

Smartphone apps to measure intensity

There are several applications available for your smart phone’s camera that will accurately measure light intensity (luminous emittance) and display the results in Lux. To better understand light intensity and how it can differ dramatically from room to room or indoors to outdoors, you can measure the lighting while moving around various rooms and other environments. To measure lighting, point it toward a white sheet of paper in each environment. This will give you the reflective lighting from the white paper but since it’s the same paper in each environment, the results are pretty consistent. Pointing the smartphone camera at the subject itself results in a reflective reading which can be very inconsistent due to reflective surfaces, windows and other issues. Professional light meters have removable translucent sensor covers and can read incident light with the cover installed and reflective light without the cover. Incident lighting is the lighting falling on the subject or room. Reflective lighting is the lighting reflecting from the subject or room and can be influenced by mirrors, polished surfaces and the color of walls as well as many other factors.

Terry O’Rourke has 20+ years in retail advertising photography and videography. He specializes in creating jewelry, fashion accessory and food images for clients worldwide. 

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