Birds in Flight

An osprey has spent twenty minutes on a dead snag above the reservoir, and you have the sitting pictures. The camera is in M with your perched-bird setup, a small focus box over the head and focus under your thumb.

Then it drops. For the next half hour it will hunt over open sky and the far treeline, and almost everything that suited the branch is now wrong. The box is too small for a crossing bird, the shutter speed that froze a turning head will smear a wing, and the lens is free to hunt in to its closest distance whenever it loses the bird.

You do not fix those one at a time while the bird circles. You turn the mode dial to U1 and slide one switch on the lens. This chapter explains what that turn brings back and why.

Page numbers in parentheses point to Nikon's Z6III Reference Guide, edition 09, which matches firmware 2.00.

01.Why Flight Is a Different Job

A bird in the air crosses the frame in a second or two and changes its background as it banks, so every setting has to be chosen before the pass begins. This guide sorts camera changes into two sizes, following Recall Shooting Functions. A change inside one job, such as one bird leaving a perch, belongs on a button you hold. A change of job, such as an afternoon of perched birds becoming an afternoon of flight, belongs on the mode dial. A user setting position, U1, U2 or U3, keeps a whole camera setup and brings it back when you turn the dial to it (p. 139). Choosing an Autofocus Setup, Menus and Controls and User Settings and Settings Files all put flight on U1 and leave perched wildlife on P, S, A and M.

The last row is the one the dial cannot do for you. The limit switch is a slider on the lens barrel that no camera setting can move.

02.How Fast Is Fast Enough

Start with a concrete pass. The osprey crosses in front of you at an illustrative 10 m/s, 30 m away, with the lens at 600 mm and the shutter open for 1/2000 s. In that time the bird travels $10 \times \tfrac{1}{2000} = 0.005$ m, or 5 mm.

What counts is how far its image moves across the sensor, and that depends on how much the lens shrinks the scene. The shrinking factor is the magnification, $m$, the size of an object's image on the sensor divided by the size of the object. For a subject much farther away than the focal length, the thin-lens approximation gives $m \approx f/d$, where $f$ is the focal length and $d$ the distance. Here $m = 0.6 / 30 = 0.02$. The length of the smear in the image, $b$, is then

where $v$ is the bird's speed across your line of sight in metres per second, $t$ the exposure time in seconds, and $f$ and $d$ are in metres. For the osprey, $b = 10 \times \tfrac{1}{2000} \times 0.02 = 1.0 \times 10^{-4}$ m, which is $100\ \mu\text{m}$, a micrometre being a thousandth of a millimetre.

Compare that with one pixel. The sensor is 35.9 mm wide (p. 997) and a full-frame picture is 6048 pixels across (p. 119), so the pixel pitch, the width of one pixel, is

$$p = \frac{35.9\ \text{mm}}{6048} \approx 5.94\ \mu\text{m},$$

the figure Image Area also works out. The smear is $100 / 5.94 \approx 17$ pixels, plain to see the moment you enlarge the frame.

To make "sharp" a number, this chapter adopts a convention: a smear of 2 pixels or less counts as sharp. It is a working rule, not a Nikon figure. Rearranging Equation 1 for the longest exposure that keeps $b \le 2p$ gives

$$t \le \frac{2p\,d}{v\,f} = \frac{2 \times (5.94 \times 10^{-6}) \times 30}{10 \times 0.6} \approx 5.9 \times 10^{-5}\ \text{s},$$

about 1/16,800 s. The camera's fastest shutter speed is 1/16000 s, with the electronic shutter only (p. 142), and even that leaves $b = 12.5\ \mu\text{m}$, about 2.1 pixels. Shutter speed alone cannot freeze this bird, and 1/16000 s instead of 1/2000 s costs three stops of light, eight times the ISO.

The answer is to swing the camera with the bird. If the bird stays in one place in the frame, its image stops travelling across the sensor and only your tracking error remains, so $v$ in Equation 1 becomes the bird's speed relative to the swing. Suppose the swing is off by an illustrative 1 m/s. At 1/2000 s the smear is $1 \times \tfrac{1}{2000} \times 0.02 = 10\ \mu\text{m}$, about 1.7 pixels, inside the convention. That is why 1/2000 s works for a panned bird, and why the water behind it streaks while the bird does not.

Panning cannot help the wings, because a wingtip moves relative to the body you follow. Give the tip an illustrative 5 m/s relative to the body. At 1/2000 s it smears $50\ \mu\text{m}$, about 8.4 pixels, and holding it to 2 pixels would take about 1/8,400 s. A slightly blurred wingtip shows a wing in motion, so whether it is a fault is a matter of taste. Going to 1/4000 s halves it to about 4.2 pixels and doubles the ISO.

03.Exposure in M With Auto ISO

The exposure follows ISO and Auto ISO and Exposure Modes: mode M at 1/2000 s or faster, the aperture at f/6.3, which the lens's name, f/5.6-6.3, gives as its widest at 600 mm, and Auto ISO sensitivity control at ON with a Maximum sensitivity of 25600. In M the shutter speed and aperture stay where you put them, and Auto ISO follows the light by changing the ISO, the amplification applied to the sensor's signal.

Suppose a grey morning needs ISO 1600 at f/6.3 and 1/2000 s. Going to 1/4000 s halves the light, so Auto ISO doubles the ISO to 3200. The ceiling is $25600 / 1600 = 16 = 2^4$ times the starting value, four stops of room. Past it the camera cannot raise the ISO further and the pictures come out dark, the sign ISO and Auto ISO names for reaching it. Minimum shutter speed applies only in P and A (p. 467), so the card leaves it out.

In M with Auto ISO on, exposure compensation moves the ISO (p. 152). It runs to $\pm 5$ EV in the steps set by b2 (p. 151), here the default 1/3 EV (p. 624). Matrix metering, the default (p. 447), weighs the whole frame, and a small bird against bright sky is a dark shape in a bright picture, so ISO and Auto ISO adds +0.7 to +1 EV against sky and uses 0 or less against dark trees. b3 Easy exposure compensation does not work in M (p. 654), so on U1 compensation moves only through its button. It stays at its default Off (p. 624), as Exposure Modes recommends. Compensation is not cleared at power-off (p. 152), and U1 stores it with the shooting mode, shutter speed and aperture (p. 142), so save U1 with the value you use most and check it whenever the background changes.

Holding Fn1 on U1, where f2 offers the role there, should apply a stored group until you let go, but Nikon documents the role only in P, S, A and M (p. 707), so test it once at U1. Recall Shooting Functions stores matrix metering at $0.0$ EV, the value for a white bird against bright sky. For a darker bird against that sky, holding Fn1 drops the live $+0.7$ EV to $0.0$ EV, which in M with Auto ISO means a lower ISO and a darker bird. Hold it for white birds, or store $+0.7$ EV in the group if most of your birds are dark.

Release Modes notes that Continuous H (extended) may not keep exposure even across a burst, and Nikon suggests autoexposure lock (p. 155). The lock lives on the sub-selector centre by default (p. 149), and the Lens Fn button ships with AE/AF lock (p. 626). U1 gives both to AF-area modes, so it has no lock control. Release Modes advises holding AE lock in flight when the light is steady, and I still leave U1 without one, because the light on a flying bird changes with every turn between sky and trees. If bursts in steady light show steps in brightness, put AE lock only on a control U1 does not use and save U1 again.

04.Keeping Focus on a Bird in the Air

Choosing an Autofocus Setup sets the focus for flight, and U1 holds its choices. Continuous AF, since the bird never stops. Birds detection added in Firmware 2.00, which arrived with firmware 2.00 as Firmware History records, puts the point on a bird's face, on an eye when it finds one, and otherwise on the whole bird (p. 127). It runs only in the Wide-area modes, 3D-tracking, subject-tracking AF and Auto-area AF (p. 128).

Menus and Controls gives U1 a small area as its base without naming one. The card fills that in with the perched setup's Wide-area AF (C1), a box you size yourself from 1x1 to 21x13 focus points in FX (p. 125), which suits a bird still sitting or swimming and keeps detection running (p. 128).

Against open sky, hold the sub-selector centre. Its U1 role is the plain AF-area mode role with a Wide-area AF (L) preset: the camera uses that area while you hold it and returns to the previous mode when you let go (p. 705). The plain role does not start focusing (p. 705), so the half-press does the focusing, which is why U1 puts a6 back at Shutter/AF-ON. The large patch keeps a panned bird covered while detection finds the face inside it. Custom Setting f16 Prefer sub-selector center is OFF on U1 against a default of ON (p. 627), so you can still tilt the sub-selector to move the point while holding its centre, a pairing Nikon itself suggests for an AF-area mode role on the centre (p. 744).

Trees change the problem. Wide-area AF (L) gives priority to the nearest subject in its area (p. 124), and in front of a treeline that is often a branch. Choosing an Autofocus Setup then switches to Dynamic-area AF (L) with no detection. Nikon names that mode for fast subjects that are hard to keep framed, with birds as its example, and it works only in photo mode with Continuous AF (p. 124). It does not run detection (p. 128), so the camera focuses on the point you placed and turns to its neighbours only when the bird slips off it, as AF-Area Modes describes. On U1 the Lens Fn button holds AF-area mode with a Dynamic-area AF (L) preset, where f2 offers it there. Nikon's lens guide names four L-Fn buttons and no L-Fn2 (lens guide, p. 11), so Lens Fn button should be the entry that applies. U1 copies the role to Lens Fn2 only as insurance, since neither guide names the entry.

Once the camera has the bird, 3D-tracking with Birds is the alternative. It follows the bird you started on, beginning with the half-press or AF-ON and ending when you let go (p. 125). Nikon warns that it can lose a subject that moves very fast, is hidden or resembles its background (p. 126), and a bird diving past trees can be all three.

a3 Blocked shot AF response sets how long the camera stays with its subject when something crosses in front, from 1 (Quick), which switches readily, to 5 (Delayed), which holds on (p. 633). Use 3 for one bird and 4 when a flock or branches keep crossing it. 3D-tracking always runs at 3 (p. 633). a1 AF-C priority selection at Release fires whether or not focus is confirmed (p. 631), since a slightly soft wingbeat is still a frame. a11, the AF-assist illuminator, stays OFF, as Nikon advises near birds (p. 129).

Nikon's list of conditions that can defeat bird detection (p. 129) includes a face too small in the frame, eyes hidden by feathers and a subject moving excessively, which describes most birds in flight. For repeated false detections Nikon suggests a smaller focus area (p. 129), which on U1 means letting go of the centre and returning to the C1 box. The lens control ring carries Focus (M/A): turning it during a half-press overrides autofocus, and half-pressing again hands focus back (p. 714). When the lens has settled on the far shore, a quick twist brings focus close enough for autofocus to take the bird.

05.Why Not the Fastest Release Mode

Continuous H (extended) with the electronic shutter shoots about 20 frames per second (fps), raw or JPEG (p. 154). The high-speed frame capture + modes, C15, C30, C60 and C120, reach about 15, 30, 60 and 120 fps (p. 1000). So why stop at 20?

Frame rate matters only against what you are trying to catch, and for a bird that is the wingbeat. If the camera shoots $r$ frames a second and the wing beats $w$ times a second, the frames per wingbeat are

$$n = \frac{r}{w}.$$

Take an illustrative 3 beats a second, each lasting about 333 ms. At 20 fps the frames are 50 ms apart and $n = 20/3 \approx 6.7$, about seven wing positions per beat. Without the electronic shutter Continuous H (extended) runs at about 14 fps (p. 154), for $n \approx 4.7$. Plain Continuous H with the mechanical shutter runs at 8.1 fps (p. 154), for $n \approx 2.7$, which can miss the raised wing beat after beat. C60 gives $n = 20$, more than any edit will use.

The C modes cost a good deal for that surplus (p. 157). They record JPEGs only, at Large size, so there is no raw file to rescue a white wing. C120 crops to DX. Shutter speeds run from 1/16000 s to 1/60 s, or 1/125 s at C120, compensation takes effect only to $\pm 3$ EV, and ISO stops at 64000. Nikon also says subject detection may perform worse during high-speed frame capture + (p. 130), and for a bird detection does most of the work. So Choosing an Autofocus Setup prefers an ordinary continuous mode unless you need the pace.

One moment does need it: a take-off you cannot time. Pre-Release Capture uses C60 with JPEG fine for that, keeping frames from before the full press. U1 stores d3 Pre-release burst at the longest value offered, since the default None keeps no such frames, and Post-release burst at 1 s in place of Max., as Pre-Release Capture recommends (pp. 624, 665). The Release mode/protect button keeps its default Release mode role on U1 (p. 625). Hold it and turn the main command dial to reach C15 to C120, where pre-release capture is available (p. 156), and go back to Continuous H (extended) once the bird is up.

06.Shutter, Display and Stabilisation

Release Modes pairs Continuous H (extended) with the Electronic shutter for birds, and U1 stores d6 Shutter type at that value. Shutter Types recommends Auto for everyday use, and both hold at once, because d6 is a Custom Setting and each U position keeps its own (p. 142). The electronic shutter gives 20 fps rather than about 14 (p. 154), speeds up to 1/16000 s (p. 142), a working d15 in Continuous H (extended) (p. 679), and bursts beyond 200 frames if asked (p. 663). Auto picks between the mechanical and electronic front-curtain shutters, and the latter stops at 1/2000 s (p. 668). The cost is a row-by-row readout that can lean a fast subject, which Shutter Types' section on the electronic shutter measures.

d2 Maximum shots per burst stays at its default of 200 (p. 624), ten seconds at 20 fps. It takes 1 to 200 or no limit, and with any other shutter a burst stops at 200 regardless (p. 663). The buffer, the fast memory that holds frames until the card takes them, sets the other limit. A High efficiency★ raw file here is about 17.3 MB (pp. 1012-1013), so a three-second pass at 20 fps is $60 \times 17.3 = 1038$ MB and a full burst $200 \times 17.3 = 3460$ MB. Nikon gives the buffer as over 1000 such frames on its own 660 GB card at ISO 100, possibly fewer in some situations (pp. 1012-1013). A half-press shows how many more frames the buffer can take (p. 155), and r000 means it is full (p. 663). High ISO NR goes to Low, ISO and Auto ISO's value for feathers (p. 476), and the image area stays FX, since C120 alone forces DX (p. 157).

d14 Display on during burst stays ON, its default (p. 625), so the view stays live, where OFF would blank it (p. 678). In Continuous H (extended) and the C modes the display does not black out at each release as it does elsewhere, and d15 Release timing indicator chooses what marks a release instead (p. 679). Type A darkens the display briefly, which Nikon says makes a panned subject easier to follow. The default, Type B, draws borders around the frame instead (pp. 625, 679). Release Modes chooses Type A for birds.

Vibration reduction goes to Sport, as Stabilisation recommends. Nikon gives Normal for still subjects and Sport for fast, unpredictable ones and for panning, and both correct only movement that is not part of the pan (p. 498). The default is Normal (p. 447), and the options vary with the lens (p. 498).

07.The Lens Limit Switch

When autofocus loses a bird against empty sky, the lens searches its range for something to focus on, and every moment of that search is a moment with no usable frame. The 180-600mm's limit switch shortens it. Focus Limiter and Manual Focus describes the two positions, FULL, given as 1.3 m to infinity, and 6 m and beyond, and works out that at 600 mm the 6 m position leaves 40 percent of the focusing range to search, measured in dioptres.

U1 uses the switch at 6 m with a15 Focus limiter setting OFF. The camera's limiter takes any near and far distance from 0.1 to 999 m (p. 648), which suits a perch at a known distance, not a bird whose distance changes through every pass. Nikon also asks for the lens switch at FULL while a range is in use (p. 650). So the two take turns: on the branch, a15 with the switch at FULL, and in the air, the switch at 6 m with a15 off.

U1 stores a15 OFF, but the switch stays where you left it, so turning to U1 with it at FULL lets the lens hunt in to 2.4 m, its closest focus at 600 mm (lens guide, p. 39). A bird nearer than 6 m cannot be focused with the switch there, which on a reservoir is rarely a loss.

08.U1 in One Turn of the Dial

To reach U1 you hold the mode dial lock release and turn the dial (p. 138). The position keeps the photo shooting and video recording menus, all the Custom Settings, the shooting mode, the shutter speed in S and M, the aperture in A and M, and the exposure compensation (p. 142). That covers every row of the recipe card except the lens switch. The button roles in f2 are Custom Settings too, so U1 carries its own button map, which is how Fn1 can mean white balance in M and a recall group at U1. What a position leaves out, such as the interval timer and focus shift, holds nothing a flight setup needs (p. 143).

Set the camera up as the card says, then go to the setup menu, open Save user settings and choose Save to U1 (pp. 142-143, 810). Then write a settings file with Save/load menu settings, which copies each U position as last saved (p. 864). That order matters, as User Settings and Settings Files explains, and loading a file later overwrites U1 to U3 (p. 864). Nikon does not say whether a change made at U1 survives a turn away and back, so run that chapter's one-minute test and, until you have, save U1 again after any change you mean to keep.

In the field the change of job takes three movements: turn the dial from M to U1, slide the lens switch from FULL to 6 m, and glance at the compensation for the background. The way back reverses them. Everything else, from the area under your thumb to the shutter type, comes with the dial.

09.The Recipe

The card collects every setting above, with the value U1 stores and the reason for it.

Field recipe · Birds in flight

Birds in flight with the Nikkor Z 180-600mm, saved to U1

Exposure

Setting	Set it to	Why
Shooting mode saved in U1	M	Shutter speed and aperture stay put while Auto ISO follows the light
Shutter speed	1/2000 s or faster	Freezes a panned bird, and 1/4000 s halves wingtip smear
Aperture	f/6.3 at 600 mm	The widest the lens offers at its long end
Auto ISO sensitivity controlPhoto shooting menu > ISO sensitivity settings > Auto ISO sensitivity control	ON	The camera trades ISO for light so the shutter speed holds
Maximum sensitivityPhoto shooting menu > ISO sensitivity settings > Maximum sensitivity	25600	Four stops of room above ISO 1600, and dark frames past it
Exposure compensation	+0.7 to +1 EV against sky	Lifts a bird's shaded underside, 0 EV or less against trees
MeteringPhoto shooting menu > Metering	Matrix metering	No time to place a spot on a moving bird
Easy exposure compensationCustom settings menu > b Metering/exposure > b3 Easy exposure compensation	Off	Has no effect in M, so compensation needs its button

Focus

Setting	Set it to	Why
Focus modePhoto shooting menu > Focus mode	Continuous AF	A flying bird never stops moving
AF-area modePhoto shooting menu > AF-area mode	Wide-area AF (C1)	A small box as the base, widened by holding the sub-selector
AF/MF subject detection optionsPhoto shooting menu > AF/MF subject detection options	Birds	The point goes to the face or eye, else the whole bird
Blocked shot AF responseCustom settings menu > a Focus > a3 Focus tracking with lock-on > Blocked shot AF response	3	Raise to 4 when a flock or branches keep crossing the bird
AF-C priority selectionCustom settings menu > a Focus > a1 AF-C priority selection	Release	A slightly soft wingbeat beats a burst that pauses
AF activationCustom settings menu > a Focus > a6 AF activation	Shutter/AF-ON	The half-press focuses, so the sub-selector only swaps area
Built-in AF-assist illuminatorCustom settings menu > a Focus > a11 Built-in AF-assist illuminator	OFF	Nikon advises it off near birds
Focus limiterCustom settings menu > a Focus > a15 Focus limiter setting > Focus limiter	OFF	The lens switch sets the near limit for flight instead

Drive and Shutter

Setting	Set it to	Why
Release modePhoto shooting menu > Release mode	Continuous H (extended)	About 20 fps of raw files, nearly seven frames per wingbeat
Shutter typeCustom settings menu > d Shooting/display > d6 Shutter type	Electronic shutter	Needed for 20 fps, 1/16000 s and a working d15
Maximum shots per burstCustom settings menu > d Shooting/display > d2 Maximum shots per burst	200	Ten seconds at 20 fps, longer than any pass
Pre-release burstCustom settings menu > d Shooting/display > d3 Pre-Release Capture options > Pre-release burst	Longest value offered	The default None keeps no frames from before the press
Post-release burstCustom settings menu > d Shooting/display > d3 Pre-Release Capture options > Post-release burst	1 s	Max. would keep filling the card with empty sky
Indicator typeCustom settings menu > d Shooting/display > d15 Release timing indicator > Indicator type	Type A	The display darkens at each release, easier to follow in a pan
Vibration reductionPhoto shooting menu > Vibration reduction	Sport	Nikon's mode for panning, and it leaves the swing alone

Image and Files

Setting	Set it to	Why
Choose image areaPhoto shooting menu > Image area > Choose image area	FX (36×24)	The full frame leaves room to keep a fast bird in it
Image qualityPhoto shooting menu > Image quality settings > Image quality	RAW	Room to recover a white wing's highlights
Image quality (HSFC)Photo shooting menu > Image quality settings > Image quality (HSFC)	JPEG fine	For the C60 take-off, which records JPEGs only
RAW recordingPhoto shooting menu > RAW recording	High efficiency★	About 17.3 MB a frame, so a 3 s pass is about 1 GB
High ISO NRPhoto shooting menu > High ISO NR	Low	Keeps feather detail at the high ISOs flight needs

Controls, Lens and Saving

Setting	Set it to	Why
Prefer sub-selector centerCustom settings menu > f Controls > f16 Prefer sub-selector center	OFF	Move the point while holding the centre for Wide-area AF (L)
180-600mm limit switch	6 m	Shortens the search when focus loses the bird, slide it by hand
User setting position	U1	Saved here, then written to a settings file

The button map shows the f2 roles U1 relies on, three of them Nikon's defaults and five set for flight. Nikon says the roles on offer vary from control to control (p. 704), so confirm each one marked where offered in f2 on your own camera. The OK button keeps Select center focus point (p. 626), so one press brings a wandering point back to the middle.

Button map · Custom setting f2

Birds in flight (U1)

Custom settings menu > f Controls > f2 Custom controls (shooting)

Point at a highlighted control, or a name in the table, to match the two.

Control	Set to	Factory default	Why
Sub-selector center	AF-area mode	AE/AF lock	Hold for Wide-area AF (L) against open sky, focus stays on the half-press
Lens Fn buttonNot on the drawing	AF-area mode	AE/AF lock	Hold for Dynamic-area AF (L) in front of trees, where offered
Lens Fn2 buttonNot on the drawing	AF-area mode	AF-ON	Copy of the Lens Fn role as insurance, where offered
Fn1 button	Recall shooting functions	White balance	Matrix at 0.0 EV for a white bird against sky, where offered
AF-ON button	AF-ON	AF-ON	The default, a second way to start focus or 3D-tracking
Release mode/protect button	Release mode	Release mode	The default, hold and turn the main dial for C60 at a take-off
OK button	Select center focus point	Select center focus point	The default, one press returns the point to the middle
Lens control ringNot on the drawing	Focus (M/A)	(Varies with lens)	Twist during a half-press to pull focus off the far shore

10.Beginner Mistakes

Turning the dial and forgetting the switch. U1 stores a15 OFF but cannot slide the lens switch to 6 m. Make the switch part of the dial movement, both ways.

Keeping Wide-area AF (L) in front of trees. It favours the nearest subject (p. 124), and the branch is nearer than the bird. Hold a lens Fn button for Dynamic-area AF (L).

Carrying sky compensation into the trees. Compensation survives a power cycle (p. 152), so +1 EV from the morning sky will brighten a bird against dark trees an hour later.

Expecting raw files from C60. The C modes record JPEGs only (p. 157).

Pulling the card straight after a long burst. The access lamp can stay lit from tens of seconds to about a minute while the buffer empties, and removing the card then can lose pictures (p. 155).

11.Related Chapters

• Choosing an Autofocus Setup: the focus choices for flight and perched birds.
• Wildlife With a Long Telephoto: the perched setup the dial turns away from.
• Menus and Controls: how U1 is laid out.
• User Settings and Settings Files: saving U1 and testing persistence.
• Recall Shooting Functions: the Fn1 group and its stored compensation.
• ISO and Auto ISO: the 25600 ceiling and compensation in M.
• Release Modes: frame rates, the buffer and d15.
• Pre-Release Capture: the C60 exception for a take-off.
• Shutter Types: the electronic shutter's readout.
• Focus Limiter and Manual Focus: the lens switch and a15.
• Stabilisation: why Sport suits a pan.