Focus and tracking

Learning goal

To photograph a flying bird sharp with a long lens, you will be able to prepare the camera in advance and follow the bird from the moment it enters the frame. You will use continuous focus, an area option and, if available, bird detection together; by limiting the lens's focus range and adjusting how tightly the camera holds on to the subject, you will keep the focus from slipping to the reeds behind. You will choose the shutter speed needed to freeze movement according to the bird's size and speed, and rescue a bird left dark in front of a bright sky by adjusting the exposure. From inside a burst, you will choose the frame where the wings are at their most telling. You will also apply the same exposure logic to the face of a person paddling in front of bright water, keeping the skin in its own color.

The question

While your friend is calmly photographing the heron from inside the hide, the bird suddenly takes off and flies just above the water, parallel to the shore. They hold the shutter button down; the camera shoots many frames a second. Back home, opening the frames, they are disappointed: in some the focus is on the reeds behind, the bird a soft smudge; in some the bird looks sharp but the wings are blurred; and in a few, a pitch-black silhouette in front of the bright sky. How do you get a flying bird sharp?

Context

In the autofocus lessons you learned continuous focus, which follows the subject and keeps renewing the focus, and the camera predicting the subject's next position (Lesson 10.2). While working on detection, you saw that some cameras scan the frame and find a person, an animal or a bird by themselves (Lesson 10.4). In blur diagnosis you also tried telling apart why a frame comes out blurred, whether the focus slipped or the movement left a trail (Lesson 10.7).

A flying bird asks for all these skills at the same time. The bird is small, fast and often in front of a busy background; the lens is long, the slice of focus thin. If the camera holds on to the reeds for a moment, the bird escapes; if the shutter speed is a little too long, the wings are smeared. This lesson takes up setting up the camera for flight in advance, following the bird and choosing the right frame from inside a sequence.

Simple explanation

How is the camera prepared for flight?

For flight, continuous focus, a medium-sized area option and, if your camera has it, bird or animal detection are a good start. A single point struggles to follow a small bird, while the wide area option that uses the whole frame sometimes jumps to a branch behind. A focus limiter is a switch found on the body of many long lenses that limits the range in which the lens searches for focus, for example only between ten meters and infinity. If the bird is far away, this switch keeps the lens from hunting pointlessly toward close distances and finds focus much faster.

Tracking sensitivity is the setting that decides how tightly the camera holds on to the subject it follows: when a branch or a reed comes in front of it, whether it switches to that at once or stays on the bird for a while. On many cameras this setting can be changed on a scale. For a bird flying in front of reeds, a tight setting reduces the focus slipping to the reeds; in a flock where many birds fly at once and you want to move from one to another, on the other hand, a looser setting works. Bringing the focus in advance to near the distance where the bird will pass also saves time, so you catch the bird as soon as it enters the frame.

Which shutter speed freezes?

Freezing a flying bird often asks for a fast shutter speed. Roughly, for large birds with slow wingbeats such as a heron or an eagle, around 1/1000 keeps the body and often the wings sharp; for small birds with fast wingbeats such as a sparrow, a swallow or a kingfisher, 1/2000 or shorter may be needed. At such short times the light falls; you need to open the aperture and raise the ISO; accepting a little grain and freezing the movement is often a better trade. A slight blur at the wingtips sometimes gives a feeling of movement; this may be not a mistake but a choice.

A dark bird flying in front of a bright sky fools the camera's metering: the frame exposed for the sky turns the bird into a silhouette. Raising exposure compensation by a stop or two, or fixing the aperture and shutter speed by hand and setting the ISO for the bird's shaded feathers, rescues its detail. A white bird, for example a great egret, on the other hand, easily blows out; pulling the exposure down a little keeps the texture of the feathers. The same logic fits people too: the face of someone paddling in front of bright water goes dark when the exposure is made for the water; on dark skin this darkening can erase the detail completely, while on light skin opening the exposure for the face can blow out the shine of the water. When the metering is taken from the face, the skin stays in its real tone.

Which frame is chosen from the sequence?

Burst shooting gives many frames in flight; choosing among them the frame where the bird is at its most telling is a job for the eye. Wing position is the moment within a wingbeat when a flying bird's wings are at their most readable and most telling. With the wings fully down, the bird's body and head show clearly; with the wings up, the bird can look smaller and more scattered; with the wings spread to the side, the feathers read one by one. Which one is better isn't a rule, but has to do with what the frame wants to tell.

When choosing, looking first at whether the eye is sharp is a good start; if the eye is soft, however well the wings sit, the frame often stays weak. Frames that leave space in front of the bird, in the direction it is flying, carry the movement. Frames where the light falls on the bird's underside or on its eye show the bird more alive. Setting aside one or two frames from a sequence and deleting the rest takes courage, but it is better than carrying hundreds of nearly identical frames on the disk.

Visual evidence

The next morning in the hide, your friend prepares the camera: continuous focus, a medium-sized area, bird detection on. They set the lens's focus limiter from ten meters to infinity and bring the tracking sensitivity to a tight value. They fix the aperture at its widest opening and the shutter speed at 1/2000, and leave the ISO on auto.

When the heron takes off, they catch it the moment it enters the frame and follow it along the shore. The camera doesn't jump to the reeds; the eye is sharp. When it passes in front of the sky the bird darkens, and they raise the exposure compensation by a stop and a half. From the twenty-frame sequence they choose two frames where the wings are down and the morning light falls on the bird's underside.

That same morning a young woman paddling a canoe on the lake, dark-skinned, passes where the heron passed. Your friend watches her and waves to ask permission; the woman smiles and nods. In front of the bright water, in the first frame her face is dark; when they take the metering from her face, her skin is in its own brown, drops falling from her paddle.

Common mistakes

Summary

A flying bird is photographed sharp with a camera prepared in advance with continuous focus, a medium-sized area, bird detection, the switch that limits the lens's focus range and a tight tracking sensitivity, with a short shutter speed chosen for its size and speed, and with an exposure raised against a bright sky. From inside the sequence, the frame where the eye is sharp and the wing position most telling is chosen; the same metering logic is applied to the face of a person in front of bright water, keeping the skin in its own color.

Mini assignment

In this assignment you will practice focus tracking with flying birds.

1. Set your camera to continuous focus, a medium area option and, if available, bird detection; if your lens has a focus limiter, set it to the far range.
2. In a park, on a shore or on a pier, photograph flying gulls, pigeons or other birds at 1/1000 and 1/2000, first with the default, then with a tight tracking sensitivity.
3. Compare the frames enlarged; for birds that go dark in front of the sky raise the exposure compensation, and choose from the sequences the two frames with the most telling wing position.

Check yourself

• With which setting did the focus slip less to the background?
• At which shutter speed did the wings freeze?
• In the frames you chose, is the eye sharp, and what do the wings tell?

Glossary

Mini quiz

1. What is a focus limiter for?

• A) It narrows the range in which the lens searches for focus and speeds up focusing
• B) It limits the aperture
• C) It raises the burst rate
• D) It turns off image stabilization

2. How is tracking sensitivity set for a single bird flying in front of reeds?

• A) To the loosest value
• B) It is turned off
• C) To a tight value, so the focus doesn't slip to the reeds
• D) At random

3. Which shutter speed may be needed to freeze a small bird with fast wingbeats?

• A) 1/60
• B) 1/250
• C) 1/500
• D) 1/2000 and faster

4. Why does a dark bird in front of a bright sky turn into a silhouette?

• A) Because the lens is too long
• B) The camera exposes for the sky and darkens the bird
• C) The focus has slipped
• D) Because the wings are moving

Answers

1. A — With a distant bird, the lens is kept from hunting pointlessly toward close distances.
2. C — Tight tracking stays on the bird without switching at once to the reeds that come in front of it.
3. D — Small wings beating fast freeze only at very short times.
4. B — The metering pulls the bright sky to an average and the dark bird against it loses its detail.

Summary card

• Continuous focus, medium area, bird detection.
• Set the focus limiter to far; tighten the tracking.
• Large bird 1/1000, small bird 1/2000 and above.
• Dark bird against the sky: raise the exposure; white bird: pull it down a little.
• Choose from the sequence the frame with a sharp eye and a telling wing position; meter the face in front of bright water from the face.

Bridge to the next lesson

The heron's flight frame is much liked at the club. Your birdwatcher friend hands them a notebook: more than a hundred species have been seen on this lake alone, but most of them stop by during certain weeks of the year, passing from a distant delta or reed bed. Your friend realizes they always photograph the same bird. Where and when do you find birds? The next lesson takes up wetlands, migration seasons and the calendar birds follow over a year.