The Focus Custom Settings

A grey heron lifts off the far bank of a river and flaps low across the water. You follow it at 600 mm with the camera firing 20 frames per second (fps). Halfway across, a willow branch sweeps through the frame and hides the bird for three tenths of a second. That is six frames, and they are gone whatever you have set, because the branch is in every one of them.

The frames after the branch clears are another matter. Whether they show a sharp heron or a soft one depends on one number in the Custom Settings menu that is easy never to look at.

Autofocus (AF) is the camera driving the lens to bring the subject into focus. Its Custom Settings sit in group a, from a1 to a16. Twelve are covered here, plus AF fine-tuning options from the setup menu. The other four live elsewhere: a6 AF activation in Back-Button Focus, and a12, a15 and a16 in Focus Limiter, Saved Positions and Manual Focus. Page numbers in parentheses point to Nikon's Z6III Reference Guide (RG), edition 09, which matches firmware 2.00.

AF-S, single AF, focuses once on a half-press of the shutter-release button and holds that distance. AF-C, continuous AF, keeps refocusing while you hold the half-press. MF is manual focus. Focus Modes covers all three. The focus point is the box marking where the camera measures focus, and the AF-area mode sets its size and whether the camera may move it, as AF-Area Modes explains.

01.When the Shutter May Fire

Every full press of the shutter-release button asks the camera a question: take the picture now, or wait until focus is confirmed? Release priority takes it now, sharp or not. Focus priority waits until the camera judges the subject sharp.

Release priority never misses the moment but can hand you a soft frame. Focus priority never hands you a frame it knew was soft, but it can hold the shutter through the moment you wanted. At default settings AF-C uses release priority, AF-S uses focus priority, and MF fires whenever pressed (p. 121).

AF-C Priority Selection

Item a1 sets the rule for AF-C and offers three options (p. 631). Release fires whenever you press. Focus + release is release priority with one exception: when the subject is dark or low in contrast and you are shooting a burst, the first frame of each burst waits for focus. Focus fires only when the camera judges the subject sharp. The default is Release (p. 623).

Picture a burst through a heron's take-off. Under Release every frame is taken and a few may be soft. Under Focus, any instant without confirmed focus produces no frame, so the burst can come back with a hole where the wings were at full stretch. A soft frame can be deleted, but a frame never taken cannot be recovered. I keep Release for wildlife, perched or flying, and for other action, and use Focus + release on a dark stage, where the opening frame is the one most likely to miss.

AF-S Priority Selection

Item a2 makes the same choice for AF-S, with Release and Focus (p. 632). The default is Focus (p. 623). AF-S suits still subjects, so waiting for confirmation costs little, and I leave it there. Release helps only when the camera keeps hunting on a featureless subject and you would rather shoot than wait.

02.Focus Tracking with Lock-On

This is the setting from the heron scene, and it matters more than anything else in group a.

The Problem the Camera Cannot See

In AF-C the camera measures the distance to whatever is under the focus point many times a second and drives the lens to match. The specifications list predictive focus tracking (p. 1002), meaning the camera also estimates where a moving subject is heading and leads it.

Put numbers on the heron, as an illustration. It flies 25 m away at 10 m/s. At 20 fps, frames are

$$\frac{1}{20} = 0.05 \text{ s}$$

apart, so between frames the bird moves

$$10 \times 0.05 = 0.5 \text{ m}.$$

Its distance changes smoothly. Then the branch, 6 m away, slides under the focus point, and the reading drops by

$$25 - 6 = 19 \text{ m}$$

in a twentieth of a second. No heron does that.

Single-point AF and Dynamic-area AF are not among the modes that offer subject detection (p. 128), so in them nothing tells the camera the new object is a branch. It sees only the reading, which supports two stories. Either something has passed in front of the subject, and the lens should stay put, or you have swung onto a new, nearer subject, and the lens should go to it at once. The RG frames a3 as how quickly focus responds when something passes between camera and subject in AF-C (p. 633). In practice that is how long the camera keeps believing the first story.

Blocked Shot AF Response

a3 holds one control, Blocked shot AF response, from 1 (Quick) to 5 (Delayed), default 3 (p. 623). 5 works hardest to stay on the original subject, and 1 shifts most readily to something crossing the view (p. 633). Nikon publishes no response times, so the timings below are illustrative.

There is no separate control for how erratically the subject moves. The other levers are the AF-area mode, covered in the warning below, and Subject Detection, which governs what the camera treats as a subject.

A Branch Across a Heron, Frame by Frame

Shoot at 20 fps, the top rate of Continuous H (extended) with the electronic shutter (pp. 153, 1000). One second is 20 frames. Let the branch cover the bird from 0.35 s to 0.65 s, so the frames with the branch in them number

$$20 \times 0.3 = 6.$$

Those six are lost at every setting. The setting decides what happens next.

At 1 (Quick), the camera accepts the branch and refocuses on it. When the branch clears, the lens sits at 6 m and the heron at about 25 m. Suppose it needs a tenth of a second to swing back. That costs

$$20 \times 0.1 = 2$$

more frames, leaving

$$20 - 6 - 2 = 12$$

sharp on the bird.

At 5 (Delayed), suppose the camera keeps the lens on the heron for the whole 0.3 s, another illustrative timing. The bird is then in focus the moment the branch clears, and the count is

$$20 - 6 = 14.$$

With the mechanical shutter Continuous H (extended) tops out at 14 fps (p. 154), so every count shrinks, but the lesson holds.

The Cost of Holding On

Delayed has the mirror-image cost. What makes it ignore the branch also makes it slow to accept a change you wanted. If your aim slips and the camera accepts the far bank, a high setting then makes it hesitate when you bring the point back onto the heron. So I do not run 5 as a habit, only for a perched bird in swaying reeds. On a perch, when branches or a flock cross a flying bird, and on stage I use 4, which leans towards holding without making a slip expensive. Elsewhere the default 3 is a sensible middle. I would drop to 2 or 1 only when the thing crossing the point is the thing I want, such as one runner overtaking another.

Video has its own equivalent, Custom Setting g6 AF tracking sensitivity, from 1 (High), which shifts quickly to a new subject, to 7 (Low), which holds the original, with a default of 4 (pp. 628, 761). The video part of this guide covers it.

03.Moving the Focus Point

Six items change how the point moves when you place it and how the camera remembers it. In photo mode with the FX image area, single-point AF offers 273 points (p. 1002), and the largest custom wide-area box is 21 points by 13 (p. 125). Since

$$21 \times 13 = 273,$$

I read the grid as 21 columns by 13 rows, an inference rather than a layout Nikon prints. The multi selector or the sub-selector, the small joystick near the viewfinder, moves the point (p. 131).

Focus Points Used

Item a4 sets how many points you can choose from in every AF-area mode except Auto-area AF. All points, the default (p. 623), offers every point the mode allows. Alternating points cuts that to a quarter for quicker selection and leaves Pinpoint AF untouched (pp. 131, 634). I keep All points, because a small bird at the frame edge needs the finest placement, and a14 handles travel time.

Focus Point Wrap-Around

With ON, a point pushed past one edge reappears at the opposite edge (p. 640). With OFF, the default (p. 623), it stops. On a 21-column grid, right edge to left edge is one press with ON and

$$21 - 1 = 20$$

presses with OFF. I still leave it OFF, so that holding the selector sends the point to the edge and stops it there. The RG does not say what a held press does with ON, but I expect it would carry the point on round to the far side.

Focus Point Selection Speed

Item a14 sets how fast the point steps while you hold the multi selector or sub-selector: Low, Normal or High (p. 647). The default is Normal (p. 623), and Nikon gives no step rates. I use High, and would step down after overshooting.

Store Points by Orientation

Turn the camera for a tall frame and a subject's head moves from near the centre towards the top. Item a5 can remember separate setups for wide orientation and for tall with the camera turned a quarter-turn clockwise or counterclockwise (p. 635). Off, the default (p. 623), uses one point for all three. Focus point stores a point for each, and Focus point and AF-area mode stores the mode too (p. 636).

I use Focus point, so turning the camera brings back the point I last used for that grip. I avoid storing the mode as well, because a mode changing silently as I rotate the camera is a surprise I would rather not have mid-burst.

Focus Point Persistence

Item a7 covers one narrow case. A button carries the role AF-area mode + AF-ON, or plain AF-area mode, through Custom Setting f2 Custom controls (shooting), and while half-pressing you use it to jump from a mode where the camera picks the point, such as Auto-area AF, to one where you pick it. Auto, the default (p. 623), keeps the point the camera last chose. Off restores the point you last chose (p. 638).

I keep Auto. If I switch away from Auto-area AF mid-track, the camera has already found the bird and I want to carry on from there. Button assignment belongs to Custom Controls.

Limit AF-Area Mode Selection

Hold a button with the role Focus mode/AF-area mode and turn the sub-command dial, the dial on the front of the body (p. 51), and the camera steps through AF-area modes. Item a8 picks which ones appear (p. 639). The Fn2 button carries that role out of the box (p. 625). Every mode is ticked by default, and Single-point AF cannot be unticked (p. 623).

There are eleven: Pinpoint AF, Single-point AF, three sizes of Dynamic-area AF, four kinds of Wide-area AF, 3D-tracking and Auto-area AF. Pinpoint AF needs photo mode with AF-S (p. 123), while Dynamic-area AF and 3D-tracking need photo mode with AF-C (pp. 124-125). I keep seven, the ones the setups in Choosing an Autofocus Setup use, from widest to narrowest: Auto-area AF, Wide-area AF (L), 3D-tracking, Wide-area AF (C1), Dynamic-area AF (L), Single-point AF and Pinpoint AF. Seven modes put any mode at most six clicks from any other, if the dial does not wrap, which the Reference Guide never says. For a stage evening I trim the list to two or three, as Menus and Controls does.

04.What the Display Shows

Focus Point Display

Item a10 bundles five display choices, with defaults on p. 623.

• Manual focus mode: ON (default) shows the point at all times in MF, OFF only while you move it (p. 641).
• Dynamic-area AF assist: ON (default) also shows the surrounding points in Dynamic-area AF, OFF only the chosen one (p. 641).
• AF-C in-focus display: ON turns the point green when the camera judges focus in AF-C, OFF (default) leaves it red or yellow (p. 642).
• 3D-tracking focus point color: White (default) or Red (p. 642).
• Focus point border width added in Firmware 2.00: 1 (default) to 3 (p. 642).

I turn AF-C in-focus display on, because otherwise AF-C gives no sign of what the camera thinks. Treat the green as a hint, since the RG warns it can appear when the camera has failed to focus (p. 122). I choose Red for 3D-tracking, as a white box is easy to lose against a bright sky, and border 3, as a thin outline vanishes at a glance.

Maximum Aperture Lv

added in Firmware 2.00

Lv stands for live view, the picture the camera shows in the viewfinder or monitor before you shoot (pp. 55, 673). Item a13 arrived with firmware 2.00. On keeps that view at the lens's widest aperture, and the lens closes to your set aperture only when you press the shutter-release button fully (p. 646). The default is Off (p. 623).

The RG attaches three cautions to On (p. 646). The lens is always wide open, so pointing it at the sun or another strong light risks the camera's internal circuitry. The release may come slightly late, more so when Silent mode, the setup-menu option that switches to the electronic shutter for quiet shooting (p. 846), is on. The display may flicker around the release, or when you press a control set to Preview.

The RG does not say why this sits among the focus settings. My reading is that a wide-open lens shows the shallowest depth of field, the band of distance that looks sharp, so it is the easiest view in which to see where focus lies. That makes On worth trying for manual focus with a fast lens on a tripod. For action I leave it Off, because a burst does not need a late release.

05.The Built-In AF-Assist Illuminator

In dim light a small lamp on the front of the body can light the subject to help AF. With ON, the default (p. 623), it lights when needed in photo mode with AF-S. With OFF, it never lights, and the camera may fail to focus in poor light (p. 643).

It has more limits than its name suggests. It reaches only about 1 to 3 m, hoods should come off, and some lenses block it (p. 643). It never lights in video mode, AF-C or MF (p. 916). A Profoto A10 on-camera flash added in Firmware 2.00 set up as an AF-assist light lights regardless of a11 (p. 644). Nikon advises OFF for animals and birds, whose eyes the light may harm (p. 129), and warns against looking into it or shining it at drivers (pp. 38-39).

I keep it OFF, because I mostly photograph wildlife in AF-C, where it does nothing anyway. ON earns its place for people indoors at close range in AF-S.

06.AF Fine-Tuning

Front-Focus and Back-Focus

Put the point on a heron's eye at 10 m and suppose the sharpest plane always lands 10 cm nearer the camera (illustrative figures). The bill tip is crisp and the eye is not. That is front-focus. If the sharp plane always lands behind the eye, on the neck, that is back-focus. The key word is always. A miss that wanders from frame to frame comes from technique or tracking. A miss of the same size in the same direction, frame after frame with one lens, is what fine-tuning corrects.

Why a Mirrorless Camera Rarely Needs It

A digital single-lens reflex camera (DSLR) measures focus with a separate AF sensor, fed by light from a second mirror behind the main one. The AF sensor and the image sensor are two parts at two distances, and if their light paths differ even slightly, every focus decision carries the same offset.

The Z6III has no mirror, and its specifications describe hybrid phase-detection and contrast AF (p. 1002). As How Autofocus Works on the Sensor explains, focus is measured on the sensor that records the picture, so the two-part gap behind the classic DSLR offset does not exist. The RG does not say why the option remains. It says to use it only as required, and to tune at a distance you often shoot at, because a value set close up may work less well far away (p. 822).

The Options

The item has five parts (pp. 822-825).

• AF fine-tune switches the feature ON or OFF, default OFF (p. 805).
• Fine-tune and save lens stores a value from -20 to +20 for the attached lens. Larger values move the plane of focus farther from the camera, so front-focus calls for a positive value and back-focus for a negative one. A zoom gets separate WIDE and TELE values, and up to 40 lens types are remembered (pp. 822, 824).
• Default sets the value used for every lens with none saved (pp. 822, 825).
• List saved values shows what is stored, takes an identifier for each lens, which Z mount and some F mount lenses fill in with their serial number, and lets you delete entries (p. 823).
• Choose value for current lens picks between values saved for lenses of the same type (p. 823).

I leave it OFF, and would turn it on only after a controlled test showed one lens missing in the same direction at a distance I use, and then only through Fine-tune and save lens.

07.Recommended Settings

Birds and wildlife. AF-C with Release, a3 at 4, or 3 against open sky, the illuminator off and the in-focus display on. a3 has no effect in 3D-tracking and loses its quick end in Auto-area AF, so it earns its keep in the other AF-C modes.

People indoors. AF-C with a1 at Focus, the illuminator OFF because it lights only in AF-S (p. 643), and a5 on Focus point so tall and wide frames keep their own eye positions.

08.Beginner Mistakes

Choosing 1 because Quick sounds better. On a3, Quick means quick to abandon your subject for whatever crosses it, the opposite of what wildlife behind foliage needs.

Setting a1 to Focus for action. Bursts can come back with gaps where the action peaked.

Trusting the green box. The RG says the point can turn green when focus has failed (p. 122). Zoom in on a test frame before a session that matters.

Entering a Default fine-tune value. Default covers every lens with no saved value of its own, so a fix meant for one lens shifts focus on all of those.

09.Related Chapters

• How Autofocus Works on the Sensor: how the Z6III measures focus.
• Focus Modes: AF-S, AF-C and MF, which decide whether a1, a2 or a3 applies.
• AF-Area Modes: the eleven modes that a8 filters and that change a3.
• Subject Detection: how the camera finds people, animals and vehicles.
• Back-Button Focus: a6 AF activation and Out-of-focus release.
• Focus Limiter, Saved Positions and Manual Focus: a12, a15 and a16.
• Choosing an Autofocus Setup: complete setups built from these settings.