Outdoor Dance and Action

Late on a summer afternoon, a dancer takes four running steps across a lawn, plants a foot and rises into a split leap with a long scarf trailing from one shoulder. I am at the edge of the grass with the Tamron 70-180mm f/2.8 Di III VC VXD G2 at 180 mm, about 15 metres away, the sun low behind me. The whole leap lasts about two thirds of a second. In that time her hands sweep through an arc, the scarf flips over, and her face turns away from the camera and back.

Three things decide whether the frame at the top of that leap is worth keeping. The shutter has to be short enough that her hands come out as hands. Focus has to stay on her through a run, a rise and a turn. And a frame has to exist at the instant she peaks, which depends on the frame rate and on when the burst begins. Daylight makes all three easier than they are on a stage, and this chapter is about taking full advantage of that.

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

01.Why Daylight Is the Easy Case

On an indoor stage every setting competes for light. A faster shutter costs a stop of ISO, a smaller aperture costs another, and the noise piles up, which is why Stage Dance Stills is a chapter of compromises. Outdoors in sun the trade turns around. There is more light than the camera needs at f/2.8 and a fast shutter, so you can choose the shutter speed for the motion alone and still keep the ISO near its floor.

What remains hard is the subject. A dancer accelerates, changes shape, spins, and throws fabric across her own face. A footballer or a skateboarder poses the same problems in milder form, so although I write about dance, the recipe covers any person moving fast in good light.

02.Freezing a Moving Hand

Watch her outstretched hand during the leap. Take an illustrative speed of 5 metres per second for it, the figure Pre-Release Capture uses for a dancer's limb. During an exposure of 1/1000 s the hand travels 5 millimetres. Whether 5 mm matters depends on how many pixels it spreads across in the picture.

Motion blur is that spread: the distance the subject moves while the shutter is open, recorded as a smear along its path. The distance comes from speed and time,

where $v$ is the subject's speed in metres per second, $t$ is the exposure time in seconds, and $b$ is the distance moved in metres. To turn $b$ into pixels you need the width of the scene the frame covers at the dancer's distance. For a subject much farther away than the focal length,

where $36$ mm is the width of the sensor area the FX image area uses, as the menu name FX (36×24) states, $s$ is the distance to the subject, $f$ is the focal length, and $W$ comes out in the same unit as $s$. At $f = 180$ mm and $s = 15{,}000$ mm, $W = 36 \times 15{,}000 / 180 = 3000$ mm, so the frame spans 3 metres of lawn.

A Large FX picture is 6048 pixels wide, and raw files are always recorded at Large (p. 119). The blur in pixels is therefore

At 1/1000 s, $b = 5 \times 0.001 = 0.005$ m, or 5 mm, and $p = 5 / 3000 \times 6048 \approx 10.1$ pixels. At 1/2000 s the hand moves 2.5 mm and $p \approx 5.0$ pixels. At 1/4000 s it moves 1.25 mm and $p \approx 2.5$ pixels.

Ten pixels is a smear anyone sees on a fingertip at full size. Five is soft only to someone hunting for it. I set 1/2000 s for leaps and turns and treat 1/1000 s as the slowest I would accept. That is the speed ISO and Auto ISO settles for on a dark stage, where the light forces the compromise. In daylight nothing does.

The electronic shutter, which this recipe uses for its frame rate, adds a separate effect. It reads the sensor from top to bottom, so something crossing the frame sideways can come out leaning. What a Partially Stacked Sensor Changes works through an illustrative crossing of the full frame width at 180 mm in a quarter of a second and finds a lean of about 5 degrees. On the 3 m frame above that is 12 m/s, a sprint. The lean shrinks in proportion to speed, so a dancer running at 5 m/s, who takes about 0.6 s to cross the same frame, leans about 2 degrees. Vertical movement stretches or squashes a figure slightly instead, so the rise of a leap is safe and the sideways run is where to look for a slanted body.

03.Timing the Top of a Leap

Now follow her centre of mass, the balance point of her body, through the leap. Say it rises an illustrative half metre. Once her feet leave the ground nothing pushes her upward, so gravity alone sets the timing. The time from take-off to the top is

where $h$ is the rise in metres and $g = 9.81\ \text{m/s}^2$ is the acceleration due to gravity, with air resistance ignored. For $h = 0.5$ m, $t_{\text{up}} = \sqrt{1 / 9.81} = \sqrt{0.102} \approx 0.32$ s. The way down mirrors the way up, so the whole flight lasts about 0.64 s. Her limbs can move against that curve, which is how a dancer seems to hang in the air, but the balance point cannot.

Continuous H (extended) runs at about 20 frames a second with the electronic shutter and about 14 with the mechanical one (p. 154). At 20 fps the frames are 50 milliseconds apart and the flight holds $0.64 \times 20 \approx 12.8$ of them, so 12 or 13. Whatever their phase, one frame lands within 25 ms of the top. How far below the peak is she 25 ms away from it? Near the top her upward speed is close to zero, so the drop is

where $\tau$ is the time from the top in seconds and $\Delta h$ is the drop in metres. For $\tau = 0.025$ s, $\Delta h = 0.5 \times 9.81 \times 0.000625 \approx 0.0031$ m, about 3 mm out of a 500 mm rise. Nobody will see that. Once the burst is running, a frame at the peak is close to certain.

The burst's start is the weak point. Pre-Release Capture puts the delay between seeing something and pressing the button at about a fifth of a second. Press the moment her foot leaves the grass and the first frame arrives near 0.2 s, still about 0.12 s before the top, with three frames to come on the way up. What you lose is the take-off itself. Start the burst on the run-up and you lose nothing. With Custom Setting d2, Maximum shots per burst, at 200, as Release Modes, Frame Rates and the Buffer keeps it, a burst stops after 200 frames (p. 663). That is ten seconds at 20 fps, longer than any run, leap and landing.

04.Exposure on a Bright Afternoon

I shoot this in mode M with Auto ISO, the mode Exposure Modes gives for birds, wildlife and stage. You choose the shutter speed and the aperture, and the camera raises the ISO from the value you set whenever the picture needs more brightness (p. 161).

Suppose a cloudless midday meters f/16 at 1/125 s and ISO 100, the illustrative reading Video from First Principles also uses, roughly what the old sunny-16 rule of thumb predicts. The light reaching the sensor grows with the exposure time and with the inverse square of the f-number, so the ISO $S$ needed for a chosen shutter time $t$ and f-number $N$ is

where $t_0 = 1/125$ s and $N_0 = 16$ are the reference reading at ISO 100. At $t = 1/2000$ s and $N = 4$, $S = 100 \times 16 \times (4/16)^2 = 100 \times 16 \times 0.0625 = 100$. At the same speed and $N = 2.8$, $S = 100 \times 16 \times (2.8/16)^2 = 100 \times 16 \times 0.0306 \approx 49$.

ISO 49 is below ISO 100, the bottom of the camera's normal range (p. 159), so at f/2.8 and 1/2000 s that sun overexposes by about $\log_2(100/49) \approx 1$ stop unless something else gives. The Lo settings reach down to about ISO 50 (p. 159), but I do not count on Auto ISO to go below the value I set, and closing the aperture is simpler. The fix is f/4 at 1/2000 s, which lands at ISO 100 exactly, or f/2.8 at 1/4000 s, which needs $S \approx 98$. I take f/4. Depth of field, the zone of acceptable sharpness, grows too. By the approximation in Choosing an Autofocus Setup, with its 0.03 mm convention for the largest blur that passes as sharp, at 180 mm and 15 m it widens from about 1.2 m at f/2.8 to about 1.7 m at f/4, room for an arm flung toward the camera. When she runs into open shade, illustratively three stops darker, $S = 100 \times 2^3 = 800$, and Auto ISO goes there without being asked.

Maximum sensitivity stays at ISO 25600, the ISO chapter's ceiling for mode M, which daylight never reaches. Matrix metering reads the scene, as Metering recommends for most work. A white costume in full sun is the case to watch. In mode M with Auto ISO, exposure compensation changes the ISO the camera picks (p. 152), so dial in a third or two-thirds of a stop under if the highlights blink. Compensation survives switching the camera off (p. 152), so set it back to zero when you finish.

Nikon warns that Continuous H (extended) may not hold the same exposure across every shot of a burst at some settings, and names autoexposure lock as the cure (p. 155). Autoexposure lock, AE lock for short, freezes the exposure so it stops following the scene (p. 149). In steady sun I hold it. AE lock (hold) locks on one press and stays locked until a second press or the standby timer ends it (p. 706), so it lasts through a whole sequence without a finger on it. Release it before she moves into shade, because while the lock holds, the camera stops adjusting exposure (p. 149), and Auto ISO cannot follow her into the darker light. My base map has no spare AE lock button, so the recipe below moves one role.

Leave Tone mode at SDR. HLG, the high dynamic range option, drops Continuous H (extended) to the rate of plain Continuous H (p. 155) and can weaken subject detection (p. 130). Natural light auto white balance follows the sun as clouds pass, as White Balance recommends for dance outdoors, and Standard is the Picture Control Picture Controls and Colour gives for the same work.

05.Focus That Stays on a Dancer

Choosing an Autofocus Setup settles the focus setup for outdoor dance, and I follow it here: Continuous AF with 3D-tracking and People, Wide-area AF (L) with People as the fallback, a1 at Release, AF-ON only with out-of-focus release enabled, and the focus limiter OFF.

3D-tracking is an AF-area mode in which you place the focus point on the dancer, start focus with the AF-ON button, and the camera moves the point after her as she crosses the frame. Lifting your thumb ends tracking and puts the point back where it started (p. 125). With People chosen for subject detection, the camera finds a face and, when it can see them, an eye. If she looks away after her face has been found, the point keeps following her (p. 127).

It has limits, and dance hits several of them. Nikon warns that tracking may fail on a subject that changes visibly in size, colour or brightness, or that resembles its background (p. 126). A spin that swings a dark skirt into the light does all three. People detection may struggle when the face is very large or very small in the frame, when it is lit harshly, behind sunglasses or hair, or when the subject moves a great deal (p. 129). Outdoors that list reads like a description of an afternoon rehearsal.

So the fallback has to be one press away. AF-area mode + AF-ON is a role that, while its button is held, switches to a preset AF-area mode and focuses, and returns to the previous mode when you let go (p. 705). On my base map the sub-selector centre carries it with Wide-area AF (L), where the camera offers that role on that control. Wide-area AF (L) is a large box that still uses People detection inside it (p. 128). When tracking jumps to a branch, I move my thumb from AF-ON to the sub-selector, frame her inside the box, and carry on.

Custom Setting a6 at AF-ON only stops the shutter-release button from focusing when half-pressed (p. 637). With Out-of-focus release at Enable, the shutter fires whenever you press it, focused or not (p. 637), which is also what a1 Release means for AF-C (p. 631). A slightly soft frame beats one never taken. Custom Setting a3, Blocked shot AF response, needs no thought here, because 3D-tracking always runs it at 3 whatever you choose (p. 633). The OK button carries Select center focus point on my base map (p. 704), which puts the starting point back in the middle before the next run.

One habit matters more than any setting. Back-Button Focus explains that under AF-ON only, lifting the thumb during a burst ends 3D-tracking and resets the point, so keep the thumb down from the run-up to the landing. Lift it on purpose only when she holds a balance and you want focus to stay where it is.

06.The Lens and Stabilisation

At 15 metres the Tamron 70-180mm f/2.8 Di III VC VXD G2 frames a full figure at its long end with room for the scarf, and its f/2.8 maximum leaves headroom for evening. At its 70 mm end the same formula gives $W = 36 \times 15{,}000 / 70 \approx 7700$ mm, so the frame spans about 7.7 m of lawn, wide enough for a group without changing lenses. The Tamron 28-75mm f/2.8 Di III VXD G2 is for a small lawn where I stand much closer. The settings here do not change between them.

The Nikkor Z 180-600mm f/5.6-6.3 VR I use for birds is the wrong lens here. It starts at 180 mm, where the Tamron ends, so it cannot widen when she runs toward you. At f/5.6 it is also two stops darker than f/2.8, since $(5.6 / 2.8)^2 = 4$, and the evening and the shade both need that light.

Tamron's instructions for this lens say its VC is switched on and off from the camera's stabilisation setting, which on the Z6III is Vibration reduction, and name no modes. Nikon offers Normal, Sport and Off depending on the lens, and recommends Sport for subjects that move quickly and unpredictably and for panning (p. 498), so choose Sport if the menu offers it with the Tamron attached, and otherwise leave VR on. Vibration Reduction covers the menu in full.

07.The Burst and the Card

Custom Setting d6 at Electronic shutter is what unlocks the 20 fps rate for raw files (pp. 154, 668). Shutter Types, Rolling Shutter and Flicker recommends Auto for general use, and this recipe follows Release Modes, Frame Rates and the Buffer instead, which picks the electronic shutter for birds and outdoor dance. Daylight does not flicker, so the banding that rules the electronic shutter out under stage lights does not arise.

Raw files at High efficiency★ are about 17.3 MB each in Nikon's table (p. 1012). At 20 fps that is $17.3 \times 20 = 346$ MB of pictures every second. Nikon's table gives a buffer of over 1000 such frames in Continuous H (extended), FX, SDR and the electronic shutter, the settings this recipe uses (p. 1012), though it measured them at ISO 100 on its own 660 GB card and says the count may drop with Auto distortion control at ON (p. 1013). The 200-frame cap from d2 therefore ends a burst long before that buffer would. A three-second burst from run-up to landing is 60 frames, about $60 \times 17.3 \approx 1038$ MB, so a rehearsal of forty leaps fills about 42 GB. Release Modes, Frame Rates and the Buffer explains why I claim no burst depth for my own card.

When to Switch to C30

A leap you can see coming does not need Pre-Release Capture, as the timing above showed. The take-off itself does, and so does anything without warning: a lift that starts on a cue you cannot hear, or a stumble you want to keep. C30 shoots at 30 fps (p. 156) and, with a Pre-release burst set in d3, keeps frames from before the full press (p. 665). Pre-Release Capture chooses it for dance, with FX, JPEG fine and a two-second Post-release burst.

To switch, hold the release mode button and turn the main command dial (pp. 153, 156). Image quality (HSFC) added in Firmware 2.00 stores a separate quality for these modes (p. 156), so turning back to Continuous H (extended) brings raw back with no menu trip. Half-press as the run-up begins and press fully at the top. Under a6 AF-ON only the half-press does not focus, but it still starts the buffering that Pre-Release Capture describes, so your thumb stays on AF-ON as before.

The cost is real. C30 records JPEG only, at Large only, between 1/16000 s and 1/60 s (p. 157), and subject detection may work less well during them (p. 130). If the longest pre-release window is one second, as Pre-Release Capture reports from Nikon's figures, one press saves $30 \times (1 + 2) = 90$ frames, and at Nikon's 10.3 MB for a Large JPEG fine (p. 1012) that is about $90 \times 10.3 \approx 927$ MB. Holding the half-press for more than about 90 seconds cancels the buffering (p. 665), so lift and re-press during long pauses between runs.

08.Heat on a Long Afternoon

Nikon rates the Z6III to work up to 40 °C (p. 1009), and sun on a black camera body pushes it there sooner than the air temperature suggests. Heat, Power and Recording Limits covers the warnings. In short, keep the camera in shade between takes, switch it off during long waits, and keep a spare battery in a pocket out of the sun.

09.The Recipe

Every setting above appears in the card below.

The button map keeps my base layout for P, S, A and M, with one change. Starlight view (photo Lv) on the video record button is a night tool with nothing to do on a sunny lawn, so for daylight work that button carries AE lock (hold) instead, where the camera offers that role on it.

The roles available vary with the control (p. 704), so check each assignment in f2 before you rely on it. Custom Controls has the full base map.

10.Beginner Mistakes

Opening to f/2.8 in full sun. At 1/2000 s that asks for about ISO 49, a stop below ISO 100 (p. 159), and the frames come out bright. Close to f/4 or go to 1/4000 s.

Letting the camera choose the shutter speed. In mode A the camera sets the shutter speed, as Exposure Modes explains, and it chooses for the light, not for the hand. Mode M keeps 1/2000 s fixed while Auto ISO follows the light.

Lifting the thumb mid-burst. Under AF-ON only, letting go ends 3D-tracking and returns the point to where it started (p. 125). Keep it down from the run-up to the landing.

Using C30 for everything. It gives up raw files and may weaken subject detection (pp. 130, 157). Keep it for the moments that need it.

11.Related Chapters

• Choosing an Autofocus Setup: where this focus setup was decided.
• Back-Button Focus: the thumb on AF-ON and what lifting it does.
• Subject Detection: what People finds and when it fails.
• AF-Area Modes: 3D-tracking and Wide-area AF (L) in detail.
• Release Modes, Frame Rates and the Buffer: the 20 fps burst and the buffer behind it.
• Pre-Release Capture: C30 and the d3 windows for take-offs.
• ISO and Auto ISO: mode M with Auto ISO and its ceiling.
• What a Partially Stacked Sensor Changes: why a fast sideways run can lean.
• Custom Controls: the base button map this recipe adjusts.
• Stage Dance Stills: the same dancer under stage light.
• Dance Video on a Gimbal: filming the same rehearsal.