Equipment

Learning goal

You will be able to calculate the focal length needed to fit an athlete in the frame, starting from the size of the field and your distance to the player. You will explain why a short lens isn't enough at the edge of the field, and how a telephoto lens simplifies and softens the background while enlarging the player. You will measure the difference between a wide-aperture telephoto and a zoom with a small maximum aperture in stops, ISO and noise, and see why this difference is decisive in indoor halls. You will take into account the speed of a lens's focus motor, and build your bag according to the type of sport and the place. You will know that at high ISO, noise appears earlier in the shadows of dark skin, and value the maximum aperture for this reason too.

The question

After the game, the team captain puts the club photographer's frames side by side with your friend's. In the club photographer's frames the players fill the frame, the faces big and sharp, the stand behind a soft smudge of color. In your friend's frames, on the other hand, the players have stayed small, with spectators, signs and an exit door in the background. On top of that, in the same hall, the shadows in your friend's frames are noisy. The captain points to the long, white, heavy lens on the club photographer's camera. Why a telephoto lens at the field?

Context

In the lens section you learned that a lens's widest aperture, that is, its maximum aperture, decides how much it can do in dim light (Lesson 12.6). In the depth of field lesson you calculated that the zone of sharpness thins as the focal length gets longer and the aperture opens (Lesson 8.3). In wildlife equipment you also met the monopod that carries the weight of long lenses, and the switch that narrows the distance the focus searches (Lesson Y.2).

In wildlife, a long lens was the remedy for not being able to approach a shy animal. On the field, though, the reason is different: the photographer is tied to behind the sideline, while the play happens all over the field. In this lesson we measure what this limit asks of the equipment.

Simple explanation

How long to fill the frame with a player?

Frame-filling distance is the distance at which, with a given focal length, a player's height fills the long side of the frame. On a camera held vertically on full frame, the long side is thirty-six millimeters. To fit a two-meter player on this side, the distance is found by multiplying the focal length by the player's height and dividing by thirty-six. With seventy millimeters this distance is about four meters, with two hundred millimeters eleven meters, with four hundred millimeters twenty-two meters.

These numbers tie the field to the equipment. For someone standing at the edge of a twenty-eight-meter basketball court, the play is usually between five and fifteen meters away. A zoom between seventy and two hundred millimeters does the job here. On a hundred-meter football pitch, a player in the opposite half can be more than forty meters away. There, even four hundred millimeters enlarges the player to only half the frame. A long lens also narrows the background: a narrow angle of view takes in a small slice of the stand behind the player, and most of the scattered signs stay outside.

Why does the maximum aperture matter so much?

Aperture cost is the difference a lens with a small maximum aperture charges in ISO to hold the same shutter speed. There are two stops between an f/2.8 lens and an f/5.6 lens. In a hall where ISO 1600 is enough at f/2.8 to hold a thousandth of a second, at f/5.6 ISO 6400 is needed. An ISO four times higher means clearly more noise in the shadows. In most indoor halls this difference is the difference between a sharp, clean frame and a noisy or blurred one.

Noise isn't spread equally over everyone. Because the sensor collects less light in dark areas, noise appears there sooner. On the shadowed side of dark skin, under the chin and in the eye sockets, colored speckles start to show at a lower ISO than on light skin. A lens with a wide maximum aperture keeps the ISO low and leaves these shadows clean.

A wide aperture also thins the zone of sharpness. With two hundred millimeters and f/2.8, the zone of sharpness for a player at eleven meters is around half a meter. The player is sharp, the stand a few meters behind them a soft field of color. In the same frame f/5.6 doubles this zone and the background stays more distinct.

Is speed only the shutter speed?

A focus motor is the motor inside the lens that moves the lens groups back and forth for focus. In telephoto lenses designed for sports these motors are fast and quiet. The lens groups moving inside are also kept light. So continuous focus follows the change in the distance of a running player without delay. The slow motor of an old or cheap lens, on the other hand, can fall behind a fast break even on the best camera.

The bag is built by these three measures. For a basketball game in a hall, a zoom between seventy and two hundred millimeters at f/2.8, plus a shorter, wide-aperture lens for under the basket, is usually enough. For a football game outdoors, though, a longer lens, a monopod to carry its weight and spare batteries are needed.

Visual evidence

For the next game, your friend picks up a zoom between seventy and two hundred millimeters at f/2.8 from a rental shop. Their own lens is between fifty-five and two hundred fifty, f/5.6 at its long end.

They shoot the same break first with their own lens, at two hundred millimeters and a thousandth. The camera has raised the ISO to 6400. On the shadowed chin and in the eye sockets of the opposing team's dark-skinned center there are colored speckles. With the rented lens, at the same duration, it is ISO 1600. The same face's shadows are clean, the warm brown of their skin smooth.

When they shoot the nephew reaching for the basket eleven meters away with two hundred millimeters, the player fills the frame's height. At f/2.8, the stand behind them, the spectators and the exit door have turned into a soft field of color. On the fast break, continuous focus, with the rented lens's quiet motor, doesn't let go of the nephew's face throughout the run. Their own lens's motor had fallen behind in the last two steps.

Common mistakes

Summary

A telephoto lens is needed at the field because the photographer is tied to the sideline and the frame-filling distance for a player grows with the size of the field; a telephoto also narrows and simplifies the background. A wide aperture holds a short shutter speed at low ISO without paying the aperture cost and thins the zone of sharpness, while a fast focus motor stays on the motion's trail. A low ISO also protects the shadows of dark skin from noise.

Mini assignment

In this assignment you will measure what the lenses you have can do at a field.

1. For your longest focal length, calculate the frame-filling distance that fits an adult's height on the long side of the frame, then confirm this distance by pacing it out in a schoolyard or an empty parking lot.
2. In a dim indoor space, shoot the same moving frame at a thousandth, at your lens's widest aperture; note the ISO the camera chooses and calculate how much ISO would be gained with an aperture one stop wider.
3. Shoot two people of two different skin tones, with their consent, at the same high ISO, and compare the noise in the shadowed areas of the faces zoomed in.

Check yourself

• Did the frame-filling distance you calculated match the distance you paced out at the field?
• How many times the ISO does a difference of how many stops of maximum aperture mean?
• At high ISO, in the shadows of which face did noise appear sooner?

Glossary

Mini quiz

1. At what distance does a two-hundred-millimeter lens held vertically on full frame fill the frame with a two-meter player?

• A) At about four meters
• B) At about twenty-two meters
• C) At about eleven meters
• D) At about forty meters

2. How much does the difference between f/2.8 and f/5.6 change the ISO at the same shutter speed?

• A) It quadruples it
• B) It doubles it
• C) It halves it
• D) It doesn't change it at all

3. Why does a telephoto lens simplify the background?

• A) Because it dulls the colors
• B) Because with its narrow angle of view it takes in a small slice behind the player
• C) Because it increases the light
• D) Because it shrinks the player

4. Why does noise at high ISO appear sooner in the shadows of dark skin?

• A) Because dark skin reflects more light
• B) Because the shutter speed is short
• C) Because the lens is long
• D) Because the sensor collects less light in dark areas

Answers

1. C — Two hundred times two thousand divided by thirty-six makes about eleven thousand millimeters.
2. A — Two stops, each of them twice, means four times the ISO.
3. B — A narrow angle shows only the part of the stand right behind the player.
4. D — Where little light is collected the signal is weak and the share of noise grows.

Summary card

• Frame-filling distance: focal length × height ÷ 36 (full frame, vertical).
• Basketball: 70–200; a big field: 400 and up.
• Aperture cost: twice the ISO for every stop; f/2.8 in a hall.
• A wide aperture thins the zone of sharpness and softens the background.
• A fast focus motor; a low ISO protects the shadows of dark skin.

Bridge to the next lesson

With the rented lens the frames are sharp and clean, but your friend still misses some of the game's most important moments. The nephew passes the ball not under the basket but to the corner, and the three-point shot falls outside the frame. The club photographer, on the other hand, has already turned their lens to that corner, as if they knew in advance where the ball would go. Where will the ball go? The next lesson takes up how knowing a sport and reading the game make it possible to see the moment before it happens.