Taking color temperature

Our brains can differentiate color, but we may not notice when a shadow looks a little blue or when there’s a limited spectrum of color. When you capture a scene with a camera, however, colors become quite apparent, because different light sources have their own ways of producing color.

If you view a piece of white paper under lights ranging from an indoor light bulb to the midday sun, you still see it as white. That’s simply a function of your visual memory. The camera will record it as white, too, but it may render it with a blue or orange tinge, because the color temperature of the light may differ from what the camera is set to record.

Celsius and Fahrenheit temperatures help you determine what to wear when you leave the house; Kelvin temperatures (K), however, measure light. Kelvin color temperatures range from candlelight at 1800K to overcast sky at 11000K.

Table 7-1 lists color temperatures in Kelvins for a few common light sources.

Understanding white balance

White balance refers to setting the camera to record light at its proper color temperature. Simply put, a camera renders a white piece of paper as white when its white balance is set properly for a specific type of illumination. Many cameras, including the GoPro, adjust to the proper setting automatically, but unlike with Mother Nature, automatic settings are often fooled.

One way to counteract disparity in color is to set white balance on the camera to match a specific situation. I cover this topic in more detail in “Setting White Balance” later in this chapter.

Sunlight

The primary source of light on the planet resides an average distance of 93 million miles away. The sun provides summer pleasure, vitamin D, and sometimes redistributed energy, and did I mention it’s also the recorded image’s best friend.

When you’re making movies outdoors, the quality of sunlight changes continuously throughout the day with regard to both intensity and color. If you were to start shooting at daybreak, for example, you’d reap the benefits of soft morning light, often referred to as the Golden Hour. for its flattering illumination. That means early morning light renders much warmer than the daylight setting on your GoPro (5500 K; see “Taking color temperature,” earlier in this chapter), so it reproduces as an orange glow on the subject. It’s also coming from just above the horizon, so it’s not lighting the subject from overhead.

Even though light still flatters the subject a couple of hours into the morning, the quality of illumination begins to transform as the sun gets higher. High noon puts the sun directly overhead, producing far less warmth and harsher illumination.

Some days, the clouds roll in, making the afternoon overcast. That type of light isn’t great for the beach but not too bad for shooting a movie, thanks to the nicely diffused illumination. It lacks the warmth of early morning light, but you could tweak it in postproduction.

Later in the day, when the sun breaks through the clouds, the color balance of the scene takes on the warmth of early morning, but in the reverse direction (see Figure 7-2).

Clearly, shooting outdoors covers a wide range of color temperatures. It’s vital that you make manual adjustments when necessary, as I discuss in “Bathing in sunlight” later in this chapter.

Household lights

When it comes to indoor moviemaking, most of the time you’re going to shoot under household lighting conditions. But the game has changed with the incandescent light bulb we all knew, loved, and occasionally burned our fingers on being phased out. In its place, more economical light forms are taking over. Some share similarities with formerly bulbous light sources, while others have their own qualities.

CFL bulbs

Until very recently, most lamps used incandescent bulbs (discussed later in this chapter), but these days, you’re more likely to see compact fluorescent light (CFL) bulbs than many other types of illumination, including illuminated signs, like in Figure 7-3.

CFLs are so common now that you can find them almost everywhere, but they have many variations, which makes it hard to nail down the exact color temperature of each one. Because they produce light differently from incandescent bulbs, they’re not very predictable when it comes to shooting your movie. Instead of heating a filament to burn brightly, they produce light through a jolt of electricity that excites vapor in the tube, sharing behavior with their taller cousin, the fluorescent tube.

But ingenuity is a wonderful thing. Because these lights are so popular and cheap to operate, they’ve been engineered to create various light settings, including a full spectrum of color. That makes them great for lighting television and movie sets.

Incandescent bulbs

Incandescent light bulbs are traditional light bulbs, the ones that appear above cartoon characters’ heads whenever they have a great idea. Brightness varies from 25-watt appliance bulbs to the 60-, 75-, and 100-watt bulbs used in reading lamps. Flood lighting can go to 150 watts, but generally anything equivalent to 65 watts is more common.

Currently, incandescent bulbs are being phased out, but people have stocked up on them. Incandescent illumination is shown in Figure 7-4.

Fluorescent lights

Tubes of light seem like perfect ways to deliver illumination. These long, bright sticks are efficient, effective, and used everywhere from basements and garages to factories and offices. They make light through a jolt of electricity exciting vapor in the tube. While generally not ideal for shooting a movie, there are numerous types engineered to produce a full spectrum of color. Some are even used for television and movie lighting. Here’s what you need to know:

• Daylight-balanced tubes: While comparatively lower in output than an incandescent bulb, they offer mass illumination. Sometimes four separate tubes can produce the same output, albeit by using a wider, more collective approach.
• Mixed lighting makes a good picture: Look at any office building and notice the variations in color cast. Lighting your movie with tungsten and allowing the variations of fluorescent light in the background produces a complementary cast that works to your advantage.
• Not a harsh bone in its, the subject’s body: Because illumination comes from a wide bank of soft lamps, it produces a nice soft illumination. As a result, it hides minor blemishes, making many actors fans of it.
• No heat buildup: There’s a reason these are also known as “cool lights.” Trust me, they’re a welcome alternative, especially when using a multiple light tungsten setup in the studio or location area. Fluorescent illumination doesn’t create excess heat, and you can touch the bulbs.

Candlelight

If the sun is the Big Kahuna, candlelight is the little guy. It’s the warmest and least powerful light source (below 2000 K; refer to “Taking color temperature,” earlier in this chapter) range, and by itself, it can barely cover a foot. But candlelight is still light. A group of candles can illuminate a whole scene, lending it a warm and cozy feeling. Because the GoPro gets very close, it can work nicely for candlelit scenes.

Neon lights

Iconic neon signs such as “Bar” are glass sculptures with illuminated colored light running through their tubes. Neon is reminiscent of the night, and can render the scene with a cool tone, if not for its dominant color.

Outdoor lights (HID)

Lighting up the night takes a lot of power, and that can get expensive for whoever pays the bill. So, the goal in illuminating massive spaces is producing the most light for the least money. Many government agencies and businesses use a special kind of outdoor illumination: high-intensity discharge (HID) lights.

Like CFLs (see “CFL bulbs,” earlier in this chapter), HID lights excite a gas inside a glass tube, producing cheap, bright light. They come in three varieties:

• Sodium vapor: What you regard as a streetlight, lighting experts and city designers know as a sodium-vapor lamp on a pole. Look closely, and you’ll notice that its light has a yellowish cast (see Figure 7-5).
• Mercury vapor: Mercury-vapor lamps are far less flattering to most subjects than sodium-vapor lamps are, because they produce greenish illumination from exciting mercury gas. This color makes them problematic when it comes to video. When it comes to producing the most economical illumination, these guys are great for parking lots, garages, and even some school gymnasiums. On average, they have a color temperature of about 4200 K (see “Taking color temperature,” earlier in this chapter).
• Metal halide: Like the other HID lamps, metal-halide lamps produce light by exciting weird gases, but unlike those lamps, they also produce a full spectrum of color. And the reason for their hybrid nature? Metal-halide lamps are used to light many outdoor stadiums, and nobody wants to see anything but the richest, most saturated color when watching football on a big screen TV.

Bathing in sunlight

Here are a few ways to make the most of sunlight:

• Work the angles. I don’t mean working the angles in a grifter sort of way; rather, I mean catching sunlight from different angles.

• Shoot early or late. Sunlight becomes more intense as the sun rises higher in the sky, and color temperature increases as the day goes on. A sunny-day color temperature is about 5500K (see “Taking color temperature,” earlier in this chapter) when the sun reaches its highest point. The temperature gets warmer as dusk approaches.

  Whenever possible, it’s best to shoot your movie early in the morning or late in the afternoon. At those times, the sun is at an angle that produces the most flattering illumination and the warmest tone (refer to Figure 7-8).

• Take advantage of clouds. Although it can be beautiful, direct sunlight can also produce harsh illumination. Most people don’t like being photographed in full sunlight. But cloud cover between the sun and the subject works like a giant diffuser, bathing subjects in more-flattering light.
• Avoid shooting at noon. High Noon is a great title for a movie but not a great time to shoot it. When the sun is beating straight down on the subject, it’s not flattering and creates harsh shadows.

Managing artificial illumination

When the sun decides to call it a day, the nightscape comes to life, and individual forms of artificial lighting don’t play by the same set of rules as the sun. There are many types of artificial light, each with its own behavior (see “Shooting Under Different Light Sources,” earlier in this chapter). Here are a few potential problems of shooting under artificial light:

• Annoying color casts: Not all light sources produce a full spectrum of color, especially HID lamps (see “Outdoor lights [HID],” earlier in this chapter), which you’re likely to find on a city street or country road. Depending on the way the light source produces light, the scene can render with a yellowish or cyan tinge.

  The good news is that a meticulous white-balance setting can eliminate a color cast; the bad news is that it may deplete the scene of all color. HID lights produce a single color, so when you correct the bad color, no others are left.

• Unpredictable results: Sometimes, you don’t notice the effect of color or contrast on your smartphone’s screen until it’s too late.
• Harsh shadows: Contrasty, splotchy light creates shadows that can wreak havoc. When you adjust for these shadows, the highlights may blow out. Fix the highlights, and the middle tones become shadowy.

In the following sections, I show you how to solve problems with several types of light sources.

Handling HID lights

HID light is great for finding your car keys in a parking lot or looking at city landmarks at night, but it’s terrible for making movies.

Now, I said terrible, not impossible, because there are ways to take advantage of HIDs. Here are some ways to make this type of light work for you:

• A little goes a long way. Instead of trying to fully correct the color, just reduce it slightly. You’ll still have a color cast, but it won’t be overwhelming anymore. The footage can pass for a street scene, especially when you have supplemental light coming from stores, neon signs, or the taillights of passing cars.

• Shoot at twilight. Twilight still has ambient light and a variety of colors, including a purplish sky that looks great when you position your subject against it (see Figure 7-9).

  Because a sodium-vapor lamp’s illumination is created by excited gas, there’s nothing left to do after you correct the color. So, if you take a white balance of the scene, use a blue filter to neutralize the yellow cast, or attempt to correct it in postproduction, all that would remain is a monochromatic rendering of the subject. Unlike an incandescent light source that can be color corrected thanks to its full spectrum of color, these light forms only produce a single color. It you had to place a color temperature on this type of lamp, it would be comparable to tungsten, making it around 3000K.

It’s a good idea to take a white balance under metal-halide light. Depending on the specific type of lamp, color temperature can range from 3000K to 6000K or higher (see “Taking color temperature,” earlier in this chapter). Check and reset the white balance often.

Basic lighting

Lighting a scene means using the right materials in the right way. The way you light your scene can help establish what you’re trying to say without the audience’s noticing a thing. Viewers absorb the movie as a whole, with lighting, action, and sound quality working together to sustain their attention.

Here are the basic lights you might use:

• Key light: As the name implies, the key light is the main source of light in a scene. Whether that light is the sun, an outdoor lamp, or your light kit, its main job is to illuminate the subject. If you place the main light at a 45-degree angle from the subject, half of the subject renders in shadow, which can be quite dramatic.

• Fill light: The fill light illuminates the subject from the side not affected by the main light. Depending on the subject, you can position the fill light at a higher or lower angle than the subject to fill in the shadow areas. The fill light can also be a reflector that redirects illumination from the main light. When you’re shooting outdoors, the fill light may be a large white reflector bouncing sunlight back on the subject.

  Just make sure that the fill light doesn’t overpower the main light.

• Back light (or hair light): With the front of the subject adequately covered, you use back light to add depth to the scene and separate the subject from the background. Position this light high and off to the side, at a 45-degree angle from the subject.

Tungsten lighting

Tungsten lights are used for professional lighting in the studio and on location. This type of bulb produces light by heating the tungsten filament inside until it glows (see Figure 7-7). Studio tungsten bulbs can go as high as 1,000 watts and generally produce a color temperature of 3200 K (see “Taking color temperature,” earlier in this chapter).

Tungsten lighting comes in many forms, including the icon giant lights used on movie sets. Some tungsten lights use a glass lens called a Fresnel (developed for use in lighthouses) that maximizes the light’s potential. Studio lighting uses a combination of Fresnel lenses and reflectors to concentrate light on the subject. These lights produce a full spectrum of color like the sun and can be moved wherever they’re needed.

Nonconventional lighting

Conforming to conventional lighting is a fundamental concept of moviemaking. But what about using nonconventional lighting? You can improvise with just about anything that emits light, such as the following:

• Work lights: You may have seen work-light kits at home-improvement superstores. The lights use some form of tungsten bulbs; many kits have stands and reflectors. The light is harsh but easy to smooth out by finding a creative way to diffuse it. The kits are cheap — a bonus if you’re on a limited budget.
• Flashlight or lantern: These light sources aren’t as unbelievable or impractical as you may think. They’re self-contained, low-intensity light kits that you can use in a jam or for some creative effect.
• Television screen: If the subject is close to a television set and the GoPro is close to both, it’s hard to imagine a softer, more interesting light source than the TV screen. Just tune the set to a nonbroadcast channel and position the subject close to the screen.
• Glow sticks: They’re not bright enough for illuminating a scene, but they often work in situations in which the subject is light. Not only do they provide illumination, but their intense, saturated color makes for a great subject too.

Wait for the right light

The sun flatters subjects early in the morning and early in the evening; in the middle of the day, it’s not as effective. It’s best to shoot with your GoPro either in the early morning or later afternoon, as shown in Figure 7-10.

Once the sun goes down you have twilight — that narrow span of time between sundown and dusk. The sun is below the horizon but still emits some light providing a “sweet spot” thanks to its rich blue or purple background. But twilight lasts only 20 minutes or so, so you have to act fast.

If you have time, wait for the right light. You have only a short window of time to make the shot work.

Work with the light you have

Color casts aren’t intrinsically bad, and sometimes, they have a place. The normally unflattering cast of a mercury-vapor lamp can emulate an otherworldly experience, for example, just as a street scene lit with sodium-vapor can lend warmth to a subject. (I cover both types of lighting in “Outdoor lights [HID],” earlier in this chapter.)

When the sun goes down, artificial light dominates the scene. Sometimes it does so in an unflattering way, with each light source producing a dominant color of illumination. Separately, this artificial light is problematic because it produces a single-color cast. But when you combine artificial light sources, they collectively show various colors. Put artificial light against a twilight sky, and you have something unique and often beautiful.

Use colored gels

Gels work wonders when you want to adjust the color of a scene, do something creative, or make a statement. You can use a colored gel over a light to spice up the background.

Avoid light pollution

Pollution doesn’t apply just to dirty beaches and belching factory pipes; it also refers to the interplay among lights in a scene. One light can spill to the coverage area of the next, producing hot spots, color variations, and odd shadows. In addition, it’s likely to create lens flare (see the nearby sidebar) because the GoPro captures such a wide view.

In a perfect world, having the light at your back is the ideal way to use a GoPro, but it’s not always possible to do so. That’s why it’s important to strategically place your camera and monitor the scene before recording to prevent light pollution.

Light the scene efficiently

Sometimes, a portion of the light source doesn’t reach the subject, either because it strays out of the way due to improper bouncing or isn’t bright enough. Make sure that the light is properly directed to the subject and close enough to be effective.

Deal with problematic ambient light

Whether it’s a window leaking bright light or a glaring streetlamp, stray light can ruin your shot. Combat it by repositioning the camera or blocking the offending light with a card, sheet, or anything else that prevents it from reaching your subject.