Mixed light

Learning goal

When there are two lights of different colors in the same frame, you will be able to decide deliberately which one to show in the right color. You will explain with the mired difference between the two sources why a single white balance can't show both sources neutral at once, choose the dominant light, the one that lights the face most or matters most for the story, and set the white balance for it, carry out source elimination by switching off or blocking the unwanted source, achieve a move to one source by bringing the person closer to a source, use the contrast of the two colors as a means of expression through deliberate color contrast, and correct the color of an area separately with local white balance in editing. You will see how two-colored light splits a face in two on different skin tones, and complete the module's project with natural light and a reflector only.

The question

In the evening you are in a restaurant in the seaside town with your cousins. You have sat down at the table by the window: the last blue light of the evening comes in through the glass, while the old bulbs hanging from the ceiling give off a warm, orange light. You shoot your cousin; the half of their face turned toward the window is wrapped in a cold blue, the half turned toward the bulbs in a warm orange. When you set the white balance for the window, the other half of the face and the whole restaurant drown in orange; when you set it for the bulbs, this time the window side turns ice blue.

What if there are two different colors of light in one frame? Is it possible to show both colors right at once, and if not, which one should you give up? In this lesson we will talk about making decisions in scenes where natural light mixes with artificial light, and the module's last step.

Context

Natural light rarely comes alone. Inside a house window light mixes with a bulb, in a market daylight with shop lamps, at an evening meal the last blue of the sky with candlelight. In Lesson 11.2 we saw that white balance is set for a single color of light, and in Lesson 16.6 how mixed light spoils a face in the city at night. This lesson, as the last step of shaping natural light, tells how to make a systematic decision in scenes where daylight and artificial light meet.

This decision has no single right answer. Sometimes keeping both colors carries the mood of the scene; sometimes the face looking natural in a single color matters more than anything. What matters is not leaving the result to the camera's automatic setting or to chance, and knowing which light was chosen and why.

Simple explanation

Why isn't a single white balance enough?

White balance corrects all the colors in a photo for a single color of light. If there are sources of two different colors in the frame, the correction can only make one of them neutral; the other stays either warmer or cooler. Measuring the difference between the two sources in mireds, the unit you know from the color temperature lesson, shows how big the difference is. A bulb of about 2700 kelvin is around 370 mireds, and daylight of 5500 kelvin around 180 mireds; the difference of about 190 mireds between them is big enough that even the eye notices it at once.

The eye, however, largely ignores this difference: when we walk into the restaurant, the brain adapts to the dominant light and perceives the two colors as closer. The camera doesn't make this adaptation; it records the two colors as they are. That is why a scene with mixed light, even if it looks fine to the eye, can produce in the photo an image that splits a face in two, half blue and half orange.

How is the dominant light chosen?

The dominant light is the light that lights the most important area of the frame most, most often the face, or that is most meaningful for the story, and the white balance is set for it. If window light lights the face, the white balance is set for daylight and the bulbs behind stay as warm, orange accents; if a bulb lights the face, the white balance is set for the bulb and the window becomes a cold area showing the blue evening outside. Both are legitimate; what matters is that the face looks natural in a single color.

Source elimination is switching off, blocking or reducing the effect of an unwanted source in the frame. Switching off the ceiling lamp, drawing a curtain, putting a person's back or a menu in front of a lamp most often solves the problem at its root. Moving to one source, on the other hand, is making a source dominant by bringing the person closer to it; the inverse square law (Lesson 18.2) works here too: as the person gets closer to the window, window light lights the face much more than the bulb, and the other color's share on the face shrinks.

When is mixed light kept?

Deliberate color contrast is leaving lights of two different colors together on purpose, instead of correcting them, to tell the mood of the scene. The contrast between a warm interior and the blue evening outside can tell the warmth of a room and the coolness outside in the same frame. This choice is an aesthetic decision and can't be measured as right or wrong; but it most often works best when the face stands in a single light and the other color stays in the background.

In editing, local white balance is correcting the color of only a selected area of a photo separately, for example the face or a window. Many editing programs let you change the temperature and tint of only that area with a mask or a brush. This is useful especially for reducing the blueness of a window in the background. But if the two halves of a face are in two different colors, blending the transition zone naturally is hard; moving to one source during the shoot most often gives a cleaner result.

Two-colored light creates different distortions on different skin tones. On dark skin, the orange bulb side can drift toward a reddish brown, and the blue window side toward an ashy, grayish tone; on light skin, the blue side can look pale and sickly, the orange side flushed. Whichever light is chosen as dominant, you need to enlarge the face and check that the skin stays close to its own color, and if needed bring the person a little closer to that light.

Visual evidence

In the restaurant you first notice that one of the ceiling bulbs is right above your cousin; you ask the waiter's permission and have that lamp switched off. Then you bring your cousin a little closer to the window and turn their face toward the glass: now their face is lit almost only by the evening light coming from the window. You set the white balance against the white napkin on the table; your dark-skinned cousin's face escapes the ashy veil of blue and returns to its own warm brown, with the small glint of the window in their eyes.

Behind, the other bulbs inside the restaurant stay as warm, orange points of light; you deliberately don't correct them, because they tell the warmth of the place. In the frame, a calm face in natural color and a warm interior stand side by side. In editing you only reduce the blueness of the sky outside the window a little with a local white balance correction. You don't need to touch the face; you had brought it into a single light during the shoot.

Common mistakes

Summary

A single white balance can't show sources of two different colors neutral at once; as the mired difference grows, for example between a bulb and daylight, a color split appears that the eye adapts to but the camera records as it is. The solution is to choose the dominant light that lights the face most and set the white balance for it, carry out source elimination by switching off or blocking the unwanted source, and achieve a move to one source by bringing the person closer to a source; keeping the contrast of the two colors in the background is a deliberate choice of expression. In editing, local white balance corrects an area separately, but what saves a face split into two colors most cleanly is bringing it into a single light during the shoot; this is also the safest way to protect the own color of every skin.

Mini assignment

You will first make three tries with mixed light, then complete the module's project.

1. In a room where window light and a bulb are together, shoot someone; take two frames, setting the white balance first for the window, then for the bulb.
2. Bring the face into a single light by switching off the bulb or bringing the person closer to the window, and shoot again.
3. Build deliberate color contrast in a frame: let the face be in a single light, and the other color remain as an accent in the background.
4. Module project: using natural light and a reflector only, shoot a portrait or a still life; read the light and note it, fill the shadow with the reflector while measuring, and share the result together with your light note.

Check yourself

• In the frames you shot with two different white balances, which one showed the face more naturally?
• When you moved to one source, did the color difference between the two halves of the face disappear?
• In your project frame, does the person's skin or the still life's colors stand natural, without being carried away by the color of the light?

Glossary

Mini quiz

1. When a bulb and daylight are together in the frame, why can't a single white balance show both neutral at once?

• A) The camera can't meter two lights
• B) White balance corrects only for a single color of light
• C) Daylight has no color
• D) The bulb is too bright

2. About how many mireds is the difference between a bulb of about 2700 kelvin and daylight of 5500 kelvin?

• A) 20
• B) 1000
• C) 190
• D) 2800

3. If the two halves of a face are receiving light of two different colors, what is the cleanest solution during the shoot?

• A) Switching off the unwanted source, or bringing the person closer to one source and moving to one source
• B) Leaving it to automatic white balance
• C) Raising the ISO
• D) Turning off the flash

4. A dark-skinned face in window light looks ashy and grayish because the white balance was set for the bulb. What should you do?

• A) Raise saturation
• B) Crop the frame
• C) Make the bulb even brighter
• D) Set the white balance for the window light that lights the face, and check by enlarging the face

Answers

1. B — White balance makes a single color neutral; the other color stays warm or cool.
2. C — 1,000,000 / 2700 is about 370, 1,000,000 / 5500 about 182 mireds; the difference is about 190.
3. A — A single light keeps the face in a single color; blending it in editing is hard.
4. D — The dominant light is the window light lighting the face; the white balance should be set for it.

Summary card

• A single white balance can't correct two-colored light at once; the mired difference shows its size.
• The eye adapts, the camera doesn't.
• Choose the dominant light; set the white balance for it.
• Eliminate the source or bring the person closer to one source; let the face stay in a single color.
• Color contrast in the background can be a deliberate choice; local white balance is only a helper.

Bridge to the next lesson

When the light in the restaurant isn't enough, a friend at the table turns on their phone's flash and takes a frame. In the photo on the screen the faces are pure white and flat, the shadow of the noses has fallen on the wall behind as a sharp line, there are red dots in the eyes, and the restaurant's warmly lit background has turned into a pitch-black void. Why does adding an artificial light where natural light ends give such a bad result? Why do flash photos look bad? The next lesson opens the flash and artificial light module, with the problems of direct flash on top of the camera and how giving it a direction changes everything.