Indoor arenas

Learning goal

In a sports hall with weak, flickering light, you will be able to decide, according to the type of motion, which trade-offs to make between shutter speed, aperture and ISO. You will see that some lamps brighten and dim at a speed the eye doesn't notice, that this leaves differences in brightness and color from frame to frame in a burst, and you will shrink this difference with the camera's flicker reduction setting. You will explain why, on most cameras, shooting the frame dark to escape a high ISO and brightening it later increases noise, and set the exposure correctly in the shoot. In editing you will apply noise reduction not equally over the whole frame but with a mask, strong in the background and light on faces. You will watch how colored speckles come out faster on dark skin that receives little light, and how too much reduction flattens the skin like wax.

The question

This time the game is in the sports hall in the oldest building on campus, unpainted for years. Half of the lamps hanging from the ceiling are on, the corners are dark, even the middle of the court is dim. When your friend opens the rented lens all the way and holds the duration at a thousandth, the ISO value on the camera's screen climbs to five digits. In the frames on the screen the shadows are noisy, with colored speckles on the faces. Stranger still, one frame of a burst comes out yellow, the next darker and orange, another with a dark band across its lower half. The same game, the same lamps, the same setting. How do you shoot sports in bad light?

Context

In the shutter speed lesson you saw that some lamps brighten and dim at a speed the eye doesn't notice, and that this can leave bands in the frame at short shutter speeds (Lesson 8.4). In the ISO lesson you learned that noise increases as the ISO rises, and that noise reduction can also erase fine texture (Lesson 8.6). At the first hall game you experienced that the rented f/2.8 zoom gave you two stops of breathing room, but that this breathing room has a limit too (Lesson X.2).

A sports hall brings these three problems together: insufficient light, flickering lamps and fast motion. In a well-lit hall choosing between shutter speed, aperture and ISO is easy; here, every option costs something. This lesson takes up which loss to accept and how to manage the noise that remains.

Simple explanation

Why do the lamps change from frame to frame?

Many lamps connected to the mains brighten and dim once with every wave of the electricity. On a fifty-hertz grid this means a hundred times a second, that is, a peak and a trough every hundredth of a second. The eye doesn't see it; but a short shutter speed like a thousandth of a second can land on the lamp's peak or on its trough. That is why the frames in a burst come out at different brightnesses from each other, and with some lamps in different colors. When shot with an electronic shutter that reads line by line, light and dark bands appear inside a single frame.

Flicker reduction is a setting found on some cameras that detects the lamp's brightness cycle and opens the shutter at the same point of the cycle in every frame, usually at its peak. This setting can slow the burst down very slightly, but the frames resemble each other and the colors stay consistent. If your camera has no such setting, shooting with the mechanical shutter reduces the bands. In a burst whose color shifts from frame to frame, on the other hand, you have to choose a reference frame in editing and match the others to it.

Why doesn't shooting dark and brightening later work?

The underexposure penalty is the extra noise that comes from deliberately shooting the frame dark to escape a high ISO and brightening it in editing. The real source of noise isn't the ISO setting but the scarcity of the light falling on the sensor. In a dark frame the light is just as scarce. On most cameras, raising the ISO and bringing the frame to the right brightness in the shoot gives a cleaner result than shooting dark at a low ISO and brightening by two or three stops later. In the brightened shadows the noise grows too.

When the light really isn't enough, the trade-off is made according to the type of motion. At the apex of a jump, because the body almost stops, a five-hundredth of a second can be enough. That way the ISO comes down a stop. To freeze a fast pass in the middle of the game, though, you need to stay close to a thousandth. Sometimes a little motion blur is accepted too: a sharp face and a slightly flowing ball can read better than a noisy but frozen frame. This isn't an aesthetic preference but a decision about which information matters more in that game.

How is the remaining noise managed?

Local noise reduction is applying noise reduction with a mask, region by region rather than equally over the frame. The dark stand in the background, a flat wall or the court floor in shadow can take a strong reduction; there is no detail there to lose. Faces, hands, the lettering on the jerseys and the ball's seams, on the other hand, are left with a light reduction; part of the fine texture staying as a light grain looks more natural than a face flattened like wax.

Noise doesn't look the same on every skin tone. The side of a dark face that gets no light, that is, under the chin and the temples, is where color noise shows first; the red and green speckles there spoil the skin's warmth. If a strong reduction is applied to the same face to erase luminance noise, the skin loses its texture and pores and turns into a plastic surface. On light skin, meanwhile, too much reduction turns the cheeks and forehead into a smooth smudge. That is why on faces color noise is reduced a little more strongly, and luminance noise lightly.

Visual evidence

Your friend turns on the flicker reduction setting in the camera's menu and switches the burst to the mechanical shutter. When they shoot the same fast break again, the frames are all in the same yellow tone and the same brightness; the dark band across the lower half has vanished.

For rebound and block moments they bring the duration down to a five-hundredth of a second. The ISO drops to 6400 and the bodies at the apex of the jump stay sharp. In one test they had held the ISO at 3200, shot the frame two stops dark and then brightened it. Its shadows are clearly noisier than the frame correctly exposed at 6400.

In editing they open the block frame of the center with dark brown skin. There are colored speckles on their shadowed chin. First they apply a strong noise reduction to the whole frame. The speckles go, but their face has flattened like wax, and the drops of sweat on their forehead and the texture of their brows have been erased. They undo the setting and draw a mask: strong on the dark stand, and on the face a reduction that removes the color noise but leaves the luminance noise light. In the new frame there are no speckles on the chin, and the warm brown of their skin and the drops of sweat on their forehead stand out under a fine grain.

Common mistakes

Summary

Sports in bad light are shot with light kept consistent from frame to frame by flicker reduction, an exposure set correctly in the shoot, and a deliberate trade-off made according to the type of motion; shooting dark and brightening later makes the noise grow. The remaining noise is reduced with a mask, strongly in the background and lightly on faces. That way the colored speckles in the shadows of dark skin go while the skin's texture is protected.

Mini assignment

In this assignment you will shoot a moving scene in a dim indoor space with artificial light.

1. In an indoor space with fluorescent or old lamps, shoot a fast burst at a thousandth of a second; compare the frames' brightness and color, and if your camera has flicker reduction, turn it on and repeat the burst.
2. Shoot the same scene once at a high ISO with correct exposure, and once two stops dark at a low ISO, brightening it later; compare the noise in the shadows zoomed in.
3. On a frame with a face in it, with a person who has given consent, apply a noise reduction first strongly to the whole frame, then with a mask strongly only to the background and lightly to the face, and compare the two results.

Check yourself

• With flicker reduction, do the frames of the burst resemble each other?
• Is the correctly exposed high-ISO frame or the dark frame brightened later cleaner?
• After local reduction, is the face's texture protected, and have the colored speckles gone?

Glossary

Mini quiz

1. Why do the frames of a burst come out at different brightnesses in a hall with flickering lamps?

• A) Because the camera changes focus in every frame
• B) Because the short shutter speed lands on different points of the lamp's brightness cycle
• C) Because the players move
• D) Because the ISO changes by itself

2. What does flicker reduction do?

• A) It opens the shutter at the same point of the lamp's cycle in every frame
• B) It turns off the lamps
• C) It lowers the ISO
• D) It turns the frames black and white

3. Why does shooting the frame dark and brightening it later give more noise on most cameras?

• A) Because the file is bigger
• B) Because the white balance is spoiled
• C) Because the shutter speed lengthens
• D) Because the light falling on the sensor stays just as scarce and the noise grows in the brightened shadows

4. How does local noise reduction protect a dark-skinned face?

• A) By being applied equally and strongly to the whole frame
• B) By being applied only to the background, leaving the face untouched
• C) By being applied strongly in the background, and lightly on the face, aimed at color noise
• D) By blurring the frame

Answers

1. B — The lamp brightens and dims a hundred times a second; a short duration lands on a different instant in every frame.
2. A — Because every frame is shot at the same brightness instant of the lamp, the burst stays consistent.
3. D — The source of noise is the scarcity of light; brightening later makes it grow too.
4. C — The colored speckles go, while the skin's texture stays without turning to wax.

Summary card

• Flickering lamp: flicker reduction or the mechanical shutter.
• Don't shoot dark and brighten later; raise the ISO, expose correctly in the shoot.
• Make the trade-off by the motion: a five-hundredth at the apex, shorter for a fast pass.
• Noise reduction is local: strong on the background, light on the face.
• On dark skin, remove the color noise; don't turn the texture to wax.

Bridge to the next lesson

The week after the hall, your friend goes to shoot a bicycle race organized by the club. The club photographer shoots a frame showing a cyclist sharp, and the trees and spectators behind as streaks flowing horizontally. The cyclists your friend shot at a thousandth, on the other hand, look as if they are standing still, as if parked on the sidewalk. The vehicle sharp, the background flowing: how? The next lesson takes up panning, which turns motion into streaks by following the subject with a slow shutter speed.