Low key and high key

Learning goal

By using the backdrop's tone and the lighting ratio together, you will be able to turn a studio portrait into a low-key setup, where most of the tones are dark, or a high-key setup, where most of the tones are light. Before starting to shoot, you will decide with a tonal plan where the photo's tones will gather on the histogram; for low key you will darken the backdrop, narrow the light and raise the ratio, and for high key you will keep the backdrop a few stops brighter than the subject and lower the ratio. You will see how background spill-back returning from a white backdrop to the subject eats the edges and lowers contrast, and in both setups you will set the exposure with incident light metering instead of leaving it to the camera's average. You will notice how dark and light skin can suffer edge loss at these two extremes, and keep the separation.

The question

Two ideas for the band's cover are on the table: one, a dark frame where the four members stand in a pitch-black void, half of their faces in shadow, separated only by thin lines of light. The other, a frame where the same four people look airy and clean inside a bright white brightness, almost without shadow. The band can't decide without seeing both. On the same afternoon, in the same studio, you decide to shoot both frames.

In the first try you shoot the four people lined up in front of the black backdrop with the camera's automatic exposure: the backdrop isn't black but dark gray, and the faces are washed out and close to blowing out. When you try it with the white backdrop, the opposite happens: the backdrop is a dirty gray, the faces dark. The camera tried to pull both frames toward middle gray. Dark and dramatic, or bright and clean? What builds the atmosphere at these two extremes, and why can't you trust the camera?

Context

In the histogram lesson you saw that photos whose tones are mostly dark or mostly light are deliberate types, known by the names low key and high key (Lesson 9.4). Reading these types is one thing; building them in the studio is another. In the studio these two extremes are built by using together two tools you got to know one by one in earlier lessons: the backdrop's tone and the lighting ratio.

Both extremes are choices of expression. Low key is often associated with mystery, weight, intimacy or drama; high key with openness, lightness, cleanness or joy. These associations aren't rules; a low-key portrait can also be warm and calm, a high-key portrait cold and lonely. This lesson tells the technique of the two setups and the traps of each.

Simple explanation

What is a tonal plan, and why is the exposure set by hand?

A tonal plan is deciding, before starting to shoot, where most of the photo's tones will gather: at the dark end, at the light end, or in the middle. In a low-key photo the histogram leans largely to the left, in a high-key photo largely to the right. This leaning isn't a mistake, it is the plan itself.

The camera's light meter, on the other hand, tries to pull every scene toward middle gray. If a black backdrop fills the frame the camera tends to brighten the scene, if a white backdrop fills it, to darken it; both extremes slide toward the middle. That is why in both setups the exposure isn't left to the camera. The most reliable way, as in the previous lesson, is to meter the incoming light and set the exposure for the face itself; whether the backdrop is dark or bright, the face stays at the right tone. If there is no light meter, you need to shoot a test frame with manual exposure and look at the histogram and at the face itself.

How is low key built?

A low-key setup is the studio arrangement in which most of the backdrop and the frame stay in the dark, and light falls only on selected areas of the subject. The way to build it is not to spread the light, but to restrict it. A black or dark backdrop is chosen and the subject is moved as far from it as possible; the key light's spill onto the backdrop is cut with flags. The key light is kept narrow: a gridded box or a small source makes the light fall only on the face and shoulder.

The lighting ratio is kept high for low key. The fill is either not used at all or kept very weak; the shadow side drops into darkness. To separate the subject from the dark backdrop, a thin rim light or hair light is added; these lines draw the shape of the head and shoulder inside the darkness. The power of a low-key photo comes as much from what isn't shown as from what is.

How is high key built?

A high-key setup is the studio arrangement in which most of the backdrop and the frame are in light tones, and the shadows are largely opened. A white or light backdrop is chosen, and the backdrop is kept a few stops brighter than the subject with background lights; this difference is needed for the backdrop to look completely white in the photo. The key light is large and comes from the front or slightly from the side; the lighting ratio is kept low, and the fill is strong. A clamshell pattern, or white reflectors placed on both sides of the subject, opens the shadows well.

Background spill-back is light returning to the subject from an overlit white backdrop. When you light the backdrop more than necessary, this light wraps around the subject's edges, makes the edge of the hair and shoulder shine and turns it into a white haze; it can also enter the lens and lower contrast across the whole frame. Lighting the backdrop only enough to look white, moving the subject a few steps away from the backdrop, and putting a lens hood on the lens reduce this effect. Some photographers use this slight haze on purpose, for a dreamy air; what matters is that it doesn't appear out of control.

How is skin protected at the two extremes?

Edge loss is the subject's edge disappearing into the backdrop as it comes close to the backdrop's tone. Both extremes carry this risk, and its relationship with skin is reversed. In a low-key setup, the shadow side of the face and the hair of a dark-skinned, dark-haired person can merge with the black backdrop; what remains is a face mask floating in the air. A thin rim light, a hair light, or a very slight fill on the shadow side brings the edge and the shape back. Care is also taken that the detail on the lit side of the face doesn't collapse against the left wall in the tonal plan.

In a high-key setup, on the other hand, the edges of a light-skinned, light-haired person can merge with the white backdrop; when background spill-back is added to this, the line of the face is lost. Turning the backdrop down somewhat, moving the person away from the backdrop, or putting thin black flags on both sides of the face to give the edge a slight darkness keeps the separation. Because the lit side can also blow out easily on light skin, you need to watch the overexposure warning. In a frame where people of different skin tones stand side by side, both risks can happen at the same time; you need to enlarge and check every face and every edge one by one.

Visual evidence

For the dark frame you line up the band three steps in front of black velvet. The key light, a narrow box with a grid attached, comes from the left and from above; there is no fill. Behind, on the right and the left, two gridded rim lights. You meter the faces with the light meter and set the exposure accordingly. The frame appears on the screen: the backdrop is pitch black, the left half of the four faces lit, the right half dropping into darkness. On the bassist's dark skin, the shadow side of their face and their hair have merged with the backdrop; when you open the right rim light a little, the curls of their hair and the line of their ear appear with a thin light.

For the bright frame you lower the white paper, put two flashes on the two sides of the backdrop, and light it a few stops more than the faces. In front a large clamshell, on both sides white reflectors. In the first frame the backdrop is bright white, but the edge of the keyboardist's light hair and shoulder has turned into a white haze; the light from the backdrop has wrapped around them. You turn the background lights down by half a stop and bring the band two steps forward. The backdrop is still white, but the four people's outlines now separate from it.

Common mistakes

Summary

Low key and high key are two extremes built together by the backdrop's tone and the lighting ratio, and they are decided before the shoot with a tonal plan; because the camera tries to pull both extremes toward middle gray, the exposure is set for the face with incident light metering or manually. For low key a dark backdrop, a subject far from the backdrop, narrow gridded light, a high ratio and thin rim lights are used; for high key a white backdrop a few stops brighter than the subject, a large key light from the front, a low ratio and strong fill. Background spill-back returning from a white backdrop eats the edges and lowers contrast; at both extremes edge loss becomes distinct, on dark skin in low key and on light skin in high key, and the edge of every face is checked by enlarging.

Mini assignment

In this assignment you will shoot the same person at both extremes on the same day; a dark cloth and a white sheet work as backdrops.

1. Before starting the shoot, write a tonal plan for each of the two frames: state where the histogram will gather and what tone the face will be.
2. Build the low-key frame with a dark backdrop, narrow light and no fill; shoot it once with the camera's automatic exposure and once with manual exposure set for the face, and see the difference.
3. Build the high-key frame with a white backdrop, a large light from the front and strong fill; light the backdrop once too much and once just enough, and compare the effect of background spill-back on the edges.
4. In both frames, look at whether the edge of the face and hair merges with the backdrop, and write next to the lighting diagram what you changed to keep the edge.

Check yourself

• Looking at a scene, can you say in advance in which direction the camera will shift the exposure?
• Can you explain the choices of backdrop, ratio and light size for low key and high key?
• At both extremes, did you check that the edge of the face and hair doesn't merge with the backdrop?

Glossary

Mini quiz

1. Why does a low-key frame shot with the camera's automatic exposure in front of a black backdrop come out with a dark gray backdrop and washed-out faces?

• A) Because the black backdrop reflects light
• B) Because the white balance breaks
• C) Because the camera raises the exposure to pull the scene toward middle gray
• D) Because the lighting ratio is low

2. In a high-key setup, what is needed for the white backdrop to look completely white in the photo?

• A) Keeping the backdrop a few stops brighter than the subject
• B) The backdrop receiving the same light as the subject
• C) Not lighting the backdrop at all
• D) Sticking the subject to the backdrop

3. Which is one of the ways of reducing background spill-back?

• A) Lighting the backdrop even more
• B) Leaning the group against the white paper
• C) Removing the lens hood
• D) Lighting the backdrop only enough to look white and moving the subject away from the backdrop

4. In a low-key portrait, the hair and the shadow side of the face of a dark-skinned, dark-haired person merge with the black backdrop. Which is the most fitting correction?

• A) Replace the backdrop with white
• B) Add a thin rim or hair light, or give the shadow side a very slight fill
• C) Cut the exposure by two stops
• D) Remove the key light's grid

Answers

1. C — The light meter tries to pull the black filling the frame toward middle gray and raises the exposure.
2. A — When the backdrop is a few stops brighter than the subject, it reaches white at an exposure set for the face.
3. D — An overlit backdrop sends back more light; distance also reduces the light returning to the subject.
4. B — A rim or hair light separates the head's shape from the backdrop, and a slight fill keeps detail on the shadow side.

Summary card

• Make a tonal plan before the shoot: where will the histogram gather?
• The camera pulls both extremes toward middle gray; set the exposure for the face, with a meter or manually.
• Low key: dark backdrop, narrow light, high ratio, thin rim light.
• High key: white backdrop a few stops brighter, large light, low ratio; watch for background spill-back.
• Edge loss exists at both extremes; check the edge of every face by enlarging.

Bridge to the next lesson

The studio where you shot the band's cover was large, with many lights and backdrops in rolls. After the cover was done, the drummer asked: without any of these, in their own small room, with a few cheap pieces, could they shoot similar portraits? In a room with a low ceiling and narrow walls, with a single window and a lamp or two, how far can you go? Can you set up a studio at home? The next lesson tells about a setup that works on a low budget and in a small space, and completes the module's project.