Portrait

A friend sits on the back step with a mug in both hands, half turned toward the garden. The late light comes off a pale sky behind you and falls soft on her face, and three metres behind her the garden is a clutter of hose reel, shed door and a neighbour's washing line. You turn the mode dial to U2, lift the camera with the Nikkor Z 85mm f/1.8 S on it, and a small box settles on her nearer eye.

Before the first frame she holds a sheet of white paper without optical brighteners beside her cheek and you measure the light from it. Then you talk, she laughs, and you shoot in short bursts. Afterwards her near eye is sharp to the lashes, her skin is the colour it looked on the step, and the washing line has become a few pale shapes nobody would recognise.

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

01.What the 85mm Does for a Face

Frame the same face twice so that head and shoulders fill the frame the same way, about 60 cm of subject across the long side. With the Nikkor Z 40mm f/2 you stand about 0.71 m away, and with the Nikkor Z 85mm f/1.8 S about 1.5 m away. In the first picture the nose looks large and the ears fall back. In the second the face looks the way it does across a table.

The cause is distance, not focal length. A part of the face nearer the camera is drawn larger, in proportion to how much nearer it is. Let $s$ be the distance from the lens to the ears and $d$ how far the tip of the nose stands in front of them, both in millimetres. The nose is then magnified more than the ears by the ratio $r = s/(s - d)$. Taking $d = 100$ mm as an illustrative figure for an adult face, an assumption and not a measurement,

$$r_{40} = \frac{707}{707 - 100} \approx 1.165, \qquad r_{85} = \frac{1500}{1500 - 100} \approx 1.071$$

From 0.71 m the nose is drawn 16.5% too large for the ears, and from 1.5 m only 7.1%. The focal length matters because it decides where you stand for a given framing. I like 1.5 m because it is ordinary talking distance, and the lens stays out of her face.

Nikon's product page for the lens gives a minimum focus distance of 0.8 m from the focal plane, a maximum reproduction ratio of 0.12x, nine diaphragm blades with a rounded opening, and a smallest aperture of f/16. At 0.12x the sensor's 35.9 mm long side (p. 997) spans $35.9 / 0.12 \approx 299$ mm of subject, a tight crop of eyes and mouth.

02.How Much the Background Melts

Back on the porch, the friend is 1.5 m from the lens and the garden 3 m behind her, so 4.5 m from the lens, with the lens at f/1.8. A drop of water on the hose reel catching the sky does not land on the sensor as a point. It lands as a disc about 1.89 mm across. The FX image is 6048 pixels wide (p. 119) across a sensor 35.9 mm wide (p. 997), so each pixel is about 0.00594 mm and the disc spans about 319 pixels. Every point in the garden spreads the same way, and the overlapping discs are the soft wash in the picture.

Light from the eye, which is in focus, converges to a point exactly on the sensor. Light from the farther background converges a little in front of the sensor, crosses, and spreads again, so it arrives as a disc of diameter $b$, as Figure 1 shows. The yardstick is the circle of confusion $c$, the largest disc that still passes for a point when the whole picture is viewed at a normal size. This guide uses the full-frame convention $c = 0.03$ mm. A disc smaller than $c$ reads as sharp, and a disc many times $c$ reads as blur.

For a lens of focal length $f$ at f-number $N$, focused at distance $s$, with a background point at distance $D$, all in millimetres from the lens, the thin-lens model gives

$$b = \frac{f}{N} \times \frac{f}{s - f} \times \frac{D - s}{D}$$

The first factor, $f/N$, is the diameter of the aperture opening, since the f-number is the focal length divided by that diameter. The second, $f/(s - f)$, is the magnification $m$, the size of the sitter's image on the sensor divided by her real size. The third, $(D - s)/D$, is the share of the background's distance that lies behind the sitter, from 0 for a background touching her to 1 for one at infinity. For the porch, $m = 85/1415 \approx 0.0601$, so the long side covers $35.9/0.0601 \approx 598$ mm of the scene, and

$$b = \frac{85}{1.8} \times \frac{85}{1500 - 85} \times \frac{4500 - 1500}{4500} = 47.22 \times 0.0601 \times 0.667 \approx 1.89\ \text{mm}$$

That is 63 times $c$, 5.27% of the frame's width, about 319 pixels.

The formula names the levers. At f/2.8 the disc shrinks with the opening to 1.22 mm, 205 pixels, and at f/4 to 0.85 mm, 143 pixels. Move the sitter away from the garden instead, so the background is 9 m from the lens, and the third factor rises from 0.667 to 0.833, a quarter more blur at 2.36 mm. It can never pass the value for a background at infinity, 2.84 mm or 478 pixels. Often the best gain comes from moving the person rather than the dial.

03.Same Framing, Different Lenses

The formula also says which of my lenses blurs most for a head-and-shoulders frame. Fix the framing at $m = 0.06$, a long side of about 598 mm, which puts you at $s = f(1 + 1/m) \approx 17.67 f$. For a distant background the third factor is 1, so $b = m \times f/N$ and the blur depends on the opening $f/N$ alone. The last column of Table 1 puts the background a fixed 3 m behind the sitter instead.

The 85mm's 47 mm opening is more than twice the 40mm's 20 mm, so against a distant background it blurs 2.4 times as much, and only the 70-180mm at 180 mm does better. Put the background 3 m behind the sitter and that lead vanishes: at 180 mm you stand at 3.18 m, the third factor drops to $3/6.18 \approx 0.49$, and the disc comes out at 1.87 mm against the 85mm's 1.89 mm. In my judgement the 85mm is the lens for porches and living rooms, and the 70-180 earns its place outdoors, with a distant background and room to step back.

04.Two Faces in One Frame

A couple sits on a bench and she leans back, so her face is 10 cm behind his. At 2 m and f/1.8 the depth of field, the band of distance that looks sharp, is about 59.8 mm in total, as Choosing an Autofocus Setup works out, roughly 30 mm either side of the focused eye. Her face is well outside it.

Call the total depth of field $T$, the quantity earlier chapters call $D$, renamed here because $D$ is already the background distance. With the symbols above,

$$T \approx \frac{2 N c s^2}{f^2}$$

Eye detection focuses on a face, not on the gap between two faces, and the band spreads roughly evenly either side of the focus. To reach 100 mm behind his face you need about 100 mm in front too, so $T = 200$ mm. Rearranged for the f-number,

$$N \approx \frac{T f^2}{2 c s^2} = \frac{200 \times 85^2}{2 \times 0.03 \times 2000^2} = \frac{1\,445\,000}{240\,000} \approx 6.02$$

The nearest standard third-stop value at or above 6.02 is f/6.3, and the exact thin-lens limits at f/6.3 put the band from 95 mm in front of his face to 105 mm behind it, which takes in hers. The price is light. From f/1.8 to f/6.3 is eleven third-stops, so with the shutter speed held the sensitivity rises $2^{11/3} \approx 12.7$ times, and ISO 400 becomes about ISO 5000.

The other answer is to move the people. Seat them with both faces the same distance from the camera and the depth needed is that of one face. At 2 m and f/2.8, $T \approx (2 \times 2.8 \times 0.03 \times 2000^2)/85^2 \approx 93.0$ mm, enough for two faces side by side, with two and a third stops more light than f/6.3.

With two faces in the frame, Auto-area AF puts a grey point on each person it detects, marks its own choice with icons, and moves to another subject when you press left or right on the multi selector (p. 128). When you stop down for two faces, pick the nearer, because the band reaches a little further behind the focus than in front.

05.Finding the Eye

Turn one sitter to a three-quarter view and the same problem appears inside a single face. With her head turned 45 degrees her far eye sits about 45 mm further away than the near one, as Subject Detection works out, and the band at 1.5 m and f/1.8 is 33.6 mm in total. Only one eye can be sharp, and portrait convention says the nearer.

The focus setup is the portrait setup from Choosing an Autofocus Setup. Focus mode is AF-C, continuous autofocus, because a sitter who leans forward 2 cm has left the front half of a 3.4 cm band. Nikon suggests Auto-area AF for portraits (p. 125), and with subject detection on People the camera borders a detected face and moves the focus point onto an eye once it finds one (p. 127).

When the camera picks the wrong eye, Nikon warns that choosing an eye by touching the monitor may land on the other side, and points to the multi selector instead (p. 132). At the viewfinder touch Fn is quicker, because the monitor becomes a touch pad while your eye stays at the finder. Turn it ON in Custom Setting f4 and assign Switch eyes, and a tap on the touch Fn area moves focus to the other eye (p. 730). It works only while the monitor is stowed with the screen facing out (p. 730).

AF activation, Custom Setting a6, is AF-ON only with the out-of-focus release set to Disable, so the shutter-release button never focuses and the camera fires only when in focus (p. 637), and Custom Setting a1 goes to Focus, focus priority in AF-C (p. 631). Letting go of AF-ON holds focus where it is (p. 135), which is the recomposed portrait in Back-Button Focus, and my fallback when detection loses a face in profile.

Blocked shot AF response and the focus limiter stay at their defaults of 3 and OFF (p. 623). The AF-assist illuminator ships ON (p. 623) and lights only with AF-S (p. 643), so it is dark in AF-C anyway, but I turn it OFF to keep it out of a sitter's eyes if I drop into AF-S.

Nikon lists where People detection can fail: a face too large or too small in the frame, too bright or too dark, behind glasses or sunglasses, eyes hidden by hair, or a subject moving a lot (p. 129). For those frames the sub-selector centre carries AF-area mode + AF-ON with Wide-area AF (L) as its preset, where offered (p. 704). Holding it switches to that mode and starts autofocus, and letting go brings Auto-area AF back (p. 705). Detection still works in Wide-area AF (L) (p. 128), and I expect it to favour a face inside the box, though Nikon says so only for manual focus. Custom Setting a7 decides whether the box starts at the camera's last point or yours, but only while the half-press is focusing (p. 638), which AF-ON only rules out, so try it at home first.

06.Exposure for Skin

In A, aperture-priority auto, you set the f-number and the camera sets the shutter speed. A U position stores the shooting mode and, in A, the aperture (p. 142), so U2 brings back f/1.8 with everything else. On U2 the lens control ring takes the Aperture role, which f2 offers for that ring (p. 714) and Nikon's product page lists for this lens, so the f-number changes by feel at the viewfinder.

ISO follows ISO and Auto ISO: Auto ISO sensitivity control ON, a maximum of 12800, and the minimum shutter speed on Auto, which the camera sets from the focal length and which you can bias faster or slower by highlighting Auto and pressing right (p. 467). I bias it faster, because a sitter who laughs moves more than your hands do.

Metering is Matrix with Custom Setting b4, Matrix metering face detection, at its default of ON (p. 624), so the meter takes a detected face into account (p. 655), as Metering recommends.

Vibration reduction stays on Normal with Link VR to focus point ON, both defaults (p. 447), as Vibration Reduction recommends. When Auto-area AF displays several focus points, VR is optimised for the frame centre instead (p. 499), which matters only when the shutter speed is already marginal.

07.White Balance for Skin

Skin is where a colour error shows first, because everyone knows what a face should look like. A shift that passes unnoticed on a wall makes a face look sickly or sunburnt. The remedy is to measure the light falling on the face, which is what Preset manual white balance does. The camera stores up to six measured values, d-1 to d-6 (pp. 176-177).

Hold Fn1 and turn the main command dial to Preset manual and the sub-command dial to a preset, then release Fn1 briefly and press it again, and a target appears. Place it over a white or grey object held at the face, turned as the face is, and measure with a full press of the shutter-release button, OK, or a tap on the monitor (pp. 176-177). A grey card is the better target if you have one. Otherwise use a sheet of white paper without optical brighteners, because, as White Balance warns, paper with brighteners reads bluer in daylight. A reference that is too dark or too bright cannot be measured (p. 916). With an optional flash unit attached the target cannot be moved, and Nikon asks you to centre the reference (p. 177). Nikon does not say whether a radio trigger such as the Godox X3 Pro-N counts, so I centre it whenever anything sits in the hot shoe.

Preset manual suits light that holds still. When clouds keep crossing the sun, White Balance recommends Natural light auto, and with flash the Flash preset, about 5400 K (p. 165), or Auto. Because the recipe records RAW, the camera's RAW processing can still change white balance later (p. 265).

08.Skin Softening and Portrait Impression Balance

Picture a client who wants something flattering straight out of the camera by the end of the evening, with no editing. The Z6III has two tools aimed at that request, and both act only on faces.

Skin softening smooths the complexion in pictures where the camera detects a human face, at High, Normal or Low strength, or Off. It treats up to three people in a frame, and with several faces detected, left or right on the multi selector chooses the face to smooth. It cannot be combined with high-speed frame capture +, multiple exposures or HDR overlay (p. 480).

Portrait impression balance changes the colour and brightness of skin rather than its texture. You build up to three modes, each a position on a grid whose horizontal axis runs from magenta to amber and whose vertical axis is brightness, then select one to apply while shooting (pp. 481-482). It is unavailable with the monochrome and Creative Picture Controls, and Nikon cautions that it may also shift any area whose colour resembles skin (p. 482). Both tools ship Off (p. 447).

One difference decides my choice. When the camera converts a RAW file to JPEG, Portrait impression balance is among the settings you can change and Skin softening is not (p. 265), so a wrong impression can be revised in the camera afterwards while a softened JPEG keeps its smoothing. Nikon does not say whether softening affects the RAW data itself, and I do not rely on it either way.

The Picture Control does part of the same work. Nikon pitches Portrait at smooth, natural-looking skin, and Rich Tone Portrait at more vivid colour that keeps complexion and highlight detail, for files that will be edited later (p. 184). My choice, and the one Picture Controls and Colour gives, is Rich Tone Portrait with both skin tools Off. Texture removed in the camera cannot be put back, while texture kept can be smoothed in an editor, on the cheek and not on the lashes. Portrait impression balance stays Off because I correct skin tone from the RAW, and because its warning about skin-coloured areas takes in wooden doors, sand and brick. For the client who wants a finished JPEG tonight, U2 puts both tools in slots 11 and 12 of the i menu, as The i Menu sets out.

09.Files, Cards and Drive

Files follow RAW, JPEG, HEIF and Tone Mode and Image Area and Crop: RAW + JPEG/HEIF fine★ with High efficiency★ RAW, a RAW for skin work and a JPEG to share the same evening, on the full FX image area. A session with a person is hard to repeat, so the secondary slot is set to Backup, which records every picture to both cards (p. 457).

The release mode is Continuous L, which runs at 1 to 7 frames per second, set by holding the release mode button and turning the sub-command dial (p. 153). Custom Setting d1 sets the rate (p. 662) and ships at 5 fps (p. 624). I set 3 fps, as Release Modes, Frame Rates and the Buffer does for portraits, so a short burst through a laugh gives a spread of expressions without a card full of near copies.

10.With the Godox V100N

For flash I follow Flash: the Godox V100N close to the face and to one side, the 85mm in A, and the Godox X3 Pro-N trigger starting in TTL, then switched to manual so the output holds as the framing changes. For fill in hard midday sun that chapter sets Flash sync speed to 1/200 s (Auto FP), exposure compensation for flash to Background only, and the flash mode to Fill flash. Silent mode goes OFF first, as that chapter explains. White balance moves to the Flash preset or a fresh Preset manual with the reference centred.

11.The Recipe

The card gathers every setting in this chapter with its reason.

Field recipe · Portrait

Portrait

Exposure

Setting	Set it to	Why
Mode dial	U2, saved in A	Aperture priority keeps the f-number you chose for the face
Lens	Nikkor Z 85mm f/1.8 S	Fills the frame from 1.5 m, a comfortable talking distance
Aperture	f/1.8, or f/6.3 for two faces at different depths	Wide open for one face, stopped down when a second face sits behind
Auto ISO sensitivity controlPhoto shooting menu > ISO sensitivity settings > Auto ISO sensitivity control	ON	ISO follows the light while the aperture stays put
Maximum sensitivityPhoto shooting menu > ISO sensitivity settings > Maximum sensitivity	12800	A ceiling that keeps skin from turning to grain
Minimum shutter speedPhoto shooting menu > ISO sensitivity settings > Minimum shutter speed	Auto, fine-tuned faster	A sitter who laughs or leans moves faster than the lens alone needs
MeteringPhoto shooting menu > Metering	Matrix metering	Pairs with face detection to expose for the face
Matrix metering face detectionCustom settings menu > b Metering/exposure > b4 Matrix metering face detection	ON	Lets the meter weigh the detected face
Vibration reductionPhoto shooting menu > Vibration reduction	Normal	Steadies a handheld frame from a standing sitter

Focus

Setting	Set it to	Why
Focus modePhoto shooting menu > Focus mode	Continuous AF	A sitter who leans 2 cm leaves the front half of a 3.4 cm sharp zone
AF-area modePhoto shooting menu > AF-area mode	Auto-area AF	Nikon suggests it for portraits and it finds every face
AF/MF subject detection optionsPhoto shooting menu > AF/MF subject detection options	People	Moves the focus point onto a face, then an eye
AF-C priority selectionCustom settings menu > a Focus > a1 AF-C priority selection	Focus	No frame is taken until the eye is sharp
Blocked shot AF responseCustom settings menu > a Focus > a3 Focus tracking with lock-on > Blocked shot AF response	3	The default suits a still sitter
AF activationCustom settings menu > a Focus > a6 AF activation	AF-ON only (Out-of-focus release: Disable)	Thumb focuses, finger fires, and only when in focus
Built-in AF-assist illuminatorCustom settings menu > a Focus > a11 Built-in AF-assist illuminator	OFF	Keeps the lamp out of the sitter's eyes
Focus limiterCustom settings menu > a Focus > a15 Focus limiter setting > Focus limiter	OFF	The whole range stays available for close and far frames

Drive and Files

Setting	Set it to	Why
Release modePhoto shooting menu > Release mode	Continuous L	Short bursts catch the frame between blinks
CL mode shooting speedCustom settings menu > d Shooting/display > d1 CL mode shooting speed	3 fps	A spread of expressions without a card of near copies
Choose image areaPhoto shooting menu > Image area > Choose image area	FX (36×24)	The full sensor for the most blur and detail
Image qualityPhoto shooting menu > Image quality settings > Image quality	RAW + JPEG/HEIF fine★	RAW for skin edits, JPEG to share the same evening
RAW recordingPhoto shooting menu > RAW recording	High efficiency★	Smaller RAW files at the quality the file-formats chapter recommends
Secondary slot functionPhoto shooting menu > Secondary slot function	Backup	A session is hard to repeat, so every frame goes to both cards

Colour and Skin

Setting	Set it to	Why
White balancePhoto shooting menu > White balance	Preset manual	Measured off brightener-free white paper at the face
Set Picture ControlPhoto shooting menu > Set Picture Control	Rich Tone Portrait	Keeps skin and highlight detail for later editing
Skin softeningPhoto shooting menu > Skin softening	Off	Texture stays in the file and smoothing is a choice made later
Portrait impression balancePhoto shooting menu > Portrait impression balance	Off	Skin tone is corrected from the RAW, per session

Custom Settings

Setting	Set it to	Why
Enable/disable touch FnCustom settings menu > f Controls > f4 Touch Fn > Enable/disable touch Fn	ON	Turns the stowed monitor into a pad for the right thumb
Assign touch FnCustom settings menu > f Controls > f4 Touch Fn > Assign touch Fn	Switch eyes	A tap moves focus to the other eye at the viewfinder
Save user settingsSetup menu > Save user settings	Save to U2	Stores the whole setup under one position of the mode dial

The buttons are my base map from Custom Controls with the U2 change on the lens control ring. The AF-ON button, Fn1, Fn2 and the release mode button keep their default roles (pp. 625-626). The sub-selector centre carries AF-area mode + AF-ON with Wide-area AF (L), and the Illuminator button carries Silent mode for a shy sitter, both where offered, because Nikon notes that the roles on offer vary with the control (p. 704). Touch Fn lives in f4, so it is not on the map.

Button map · Custom setting f2

Portrait

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
AF-ON button	AF-ON	AF-ON	The main focus control, since a6 is AF-ON only
Sub-selector center	AF-area mode + AF-ON	AE/AF lock	Holds Wide-area AF (L) when Auto-area picks the wrong face
Fn1 button	White balance	White balance	Hold to pick and measure a Preset manual value
Fn2 button	Focus mode/AF-area mode	Focus mode/AF-area mode	A quick way out of Auto-area AF when detection struggles
Release mode/protect button	Release mode	Release mode	Hold with the sub-command dial to change the CL rate
Illuminator button	Silent mode	LCD illumination	A quiet shutter for a shy sitter, off before any flash
Lens control ringNot on the drawing	Aperture	(Varies with lens)	Sets the f-number by feel without leaving the viewfinder

12.Saving It to U2

Set everything with the mode dial on A, then choose Save user settings, Save to U2 and Save settings (pp. 142-143).

A short list of items stays out of every U position, Manage Picture Control and the storage folder among them, together with special shooting functions such as multiple exposure and pixel shift (p. 143). None belongs to this recipe. User Settings and Settings Files covers the U positions in full.

13.Beginner Mistakes

Stopping down for safety. At f/8 the porch background disc shrinks from 1.89 mm to about 0.43 mm and the garden comes back into view. For one face, f/1.8 with the eye under the point is the better bet.

Posing the sitter against a wall. Thirty centimetres in front of a wall at 1.5 m, the third factor is $300/1800 \approx 0.167$ and the disc at f/1.8 is 0.47 mm, a quarter of the porch figure. Bring the person forward before reaching for the aperture.

Letting the camera keep the far eye. Check the box before the burst. A tap on touch Fn moves it without leaving the viewfinder.

Leaving Skin softening on from the last client. The JPEG is smoothed, and in-camera RAW processing cannot change that setting (p. 265). Check slot 11 of the i menu before each session.

Measuring white balance in the wrong light. A sheet held in sun while the face sits in shade measures the sun. Hold it where the face is, turned the same way.

14.Related Chapters

• Choosing an Autofocus Setup, the portrait focus setup and the depth-of-field formula.
• Subject Detection, People detection and the three-quarter-view eye arithmetic.
• Back-Button Focus, AF-ON only and the recomposed portrait.
• White Balance, Preset manual, mireds and fine-tuning in full.
• Picture Controls and Colour, Rich Tone Portrait and the skin tools.
• The i Menu, the U2 grid with both skin tools.
• Flash, the Godox V100N portrait and fill setups.
• Custom Controls, the base button map and the U2 changes.
• User Settings and Settings Files, saving and recalling U2.