White Balance

Hold a sheet of printer paper under a living-room lamp, then carry it outside into the shadow of a building on a clear afternoon. You will call it white in both places. The Z6III will not. Nikon puts the lamp at about 3000 K and the open shade at about 8000 K (p. 164), and to a sensor that simply counts light those numbers describe two different papers, one orange and one blue.

White balance tells the camera which paper it is looking at, so that it can turn the paper back into white and carry every other colour in the frame along with it. Get it right and a dancer's skin looks like skin under a followspot. Get it wrong and a sunset is scrubbed grey, or a portrait in shade comes out cold and faintly blue.

01.Why White Light Is Not One Colour

Heat any object far enough and it glows. A stove ring glows dull red, a tungsten filament, much hotter, glows yellow-orange, and the far hotter surface of the sun gives daylight. Physicists describe this with an idealised black body, a perfect absorber whose glow depends only on its temperature. The colour temperature of a light source is the temperature of the black body whose glow matches the source's colour, measured in kelvin (K), the Celsius scale shifted so that zero is absolute zero.

Planck's law gives the shape of that glow, and Wien's displacement law gives its peak, at wavelength $\lambda_{\max} = b/T$ with $b \approx 2.898 \times 10^{-3}$ m·K. A black body at 3000 K therefore peaks near 966 nm, in the infrared, and its visible output climbs steadily toward red: by my arithmetic from Planck's law it emits about 0.24 times as much at 450 nm, a blue, as at 650 nm, a red. At 8000 K the peak moves to about 362 nm, beyond violet, and the same ratio is about 1.75. That tilt across the visible band is the whole difference between orange light and blue light.

The scale holds two surprises. The numbers run against the everyday words: the light photographers call warm, the orange of a candle or a bulb, comes from the cooler emitter, while cool blue light sits at the high end. And a high number need not mean a hotter source. Open shade is blue because the subject is lit by the blue sky rather than by the sun, and 8000 K only says that the mixture looks like a black body at that temperature.

Nikon's presets assume about 3000 K for Incandescent, 5200 K for Direct sunlight, 6000 K for Cloudy and 8000 K for Shade (pp. 164-165). Real sources vary around those figures. A standard household bulb is nearer 2400 to 2550 K, and a candle flame about 1850 K.

Fluorescent tubes and LEDs do not make their light by glowing with heat, so their light is not black-body light, and their spectra have peaks and gaps where a filament's is smooth. Makers quote a correlated colour temperature, the black-body temperature whose colour comes closest. That number cannot describe the part of the colour that falls off the black-body family, and the leftover tends to show as a green or magenta tint. This is why the camera offers a green-magenta adjustment alongside the amber-blue one that tracks colour temperature.

02.Why the Eye Adapts and the Sensor Does Not

Your visual system keeps rescaling the responses of its three kinds of cone cell so that the dominant light in a scene reads as neutral. This chromatic adaptation is why the paper looked white indoors and in shade alike, and why a lamp-lit room looks orange only for the moment after you walk in from daylight.

The sensor has no such reflex. Each photosite sits under a red, green or blue filter and counts the light that gets through, so a wall lit by tungsten gives a large red count and a small blue one every time. Nothing in the hardware knows the wall was meant to be white. The camera must either guess, which is what the Auto modes do, or be told.

03.What White Balance Does to Red, Green and Blue

The correction is multiplication. Take a grey card under tungsten light, with numbers invented to show the arithmetic rather than measured on a Z6III. Suppose the photosites under the card report average counts of 1200 for red, 1500 for green and 600 for blue. Green reads highest because, on most sensors, the green photosites respond most strongly to any ordinary light, which is my generalisation rather than a Nikon figure. A grey card reflects all colours equally, so its three channels ought to match. White balance picks a multiplier, called a gain, for each channel and keeps green as the reference: red must come up from 1200 to 1500 and blue, much further, from 600 to 1500.

As a rule, each gain is the green count divided by that channel's count, both read from something known to be neutral:

$$g_R = \frac{G}{R} = \frac{1500}{1200} = 1.25, \qquad g_G = 1, \qquad g_B = \frac{G}{B} = \frac{1500}{600} = 2.5$$

The card now comes out at 1500, 1500 and 1500, a neutral grey, and the same gains apply to every pixel. A patch of skin that recorded 1600, 1600 and 500 becomes

$$1600 \times 1.25 = 2000, \qquad 1600 \times 1 = 1600, \qquad 500 \times 2.5 = 1250,$$

a natural skin tone where the raw counts were a strong yellow-orange.

Three consequences follow. Every option on the menu is just a way of choosing three gains. One set of gains covers the whole frame, so a scene lit by two colours of light can be corrected for one of them, never both. And under tungsten the blue channel, which caught the fewest photons, is multiplied hardest. A gain scales noise along with signal, which is one reason tungsten-lit pictures can look noisier in the blues than the ISO alone suggests.

04.The Mired Scale

Equal steps in kelvin do not look like equal steps in colour. Take two pairs of lights, each 500 K apart, and divide one million by each temperature. For 2500 K that gives 400 and for 3000 K about 333, a difference of 67. For 7500 K it gives about 133 and for 8000 K exactly 125, a difference of about 8. The same 500 K is roughly eight times as big a step at the warm end, which matches what you see: the warm pair looks clearly different and the cool pair barely so.

That reciprocal is the mired, short for micro reciprocal degree. With $T$ the colour temperature in kelvin and $M$ the value in mired,

$$M = \frac{10^6}{T}.$$

Equal mired steps look like roughly equal colour steps anywhere on the scale, which is why filters for colour correction were rated in mired and why Nikon states its fine-tuning in mired (pp. 168, 171).

Two practical rules follow. Near tungsten a small kelvin change matters: 3000 K to 3200 K is about 21 mired, while 8000 K to 8500 K in shade is only about 7. And the controls feel uneven in kelvin because they are even in mired. Choose color temperature moves one mired per click of the sub-command dial (p. 172), which by my arithmetic is about 6 K near 2500 K and about 100 K near 10,000 K, so the readout should creep at the warm end and leap at the cool end.

05.The White Balance Menus

There are two menu items, one for stills and one for video.

The photo item ships at Auto with its Keep overall atmosphere sub-option (p. 446). The video item ships at Same as photo settings (p. 578), which follows the photo item (p. 589), and otherwise offers the same options (pp. 163, 173, 179). In the fully automatic shooting mode the camera handles white balance itself, while in mode P you choose it (pp. 138-139).

You rarely need the menus. White balance sits in both default i menus (pp. 83-84), and out of the box Fn1 is assigned to it in photo and video alike (pp. 74, 625, 627). Hold Fn1 and turn the main command dial to step through the options, and keep holding while turning the sub-command dial to pick a sub-option, such as an Auto variant or a fluorescent tube type (p. 163).

The Auto Modes

Auto estimates the light from the scene and sets the gains anywhere between roughly 3500 and 8000 K (p. 164). When an optional flash unit fires, it balances for the light present at that moment. Its sub-options differ in how they treat the orange of incandescent lamps. Keep white (reduce warm colors) removes it, Keep warm lighting colors preserves it, and Keep overall atmosphere, the default, removes part and leaves some warmth (p. 164). I think the default is the right everyday choice, with Keep white for neutral product shots under house lights and Keep warm lighting colors for a lamp-lit interior whose glow is the point.

Natural light auto is an automatic mode confined to daylight, about 4500 to 8000 K (p. 164). Nikon says it gives more life-like colours than Auto under natural light (p. 164) and may not give the desired results under artificial light (p. 166). Its range explains both: it cannot wander down toward tungsten values, which is right outdoors and wrong under a lamp.

To hold what either mode has chosen while you recompose, give a button the role AWB lock (hold) in Custom Setting f2, which keeps the result until a second press or the end of the standby timer (p. 706). Button assignments belong to the custom controls part of this guide.

The Fixed Presets

Direct sunlight, Cloudy, Shade, Incandescent and Flash apply the same gains whatever the frame contains. Ten frames of one scene come out identical, which an automatic mode cannot promise, and it is why Nikon advises against Auto and Natural light auto for time-lapse movies (p. 540).

Each label names the light, not the result. Shade tells the camera the light is very blue, so it adds warmth to cancel it, and used in direct sun it makes a distinctly warm picture. Nikon's general advice agrees: a higher setting gives a redder picture and a lower one a bluer picture (p. 167).

Fluorescent tubes come in different phosphor blends, so Fluorescent has three sub-options: Cool-white fluorescent, Day white fluorescent and Daylight fluorescent (p. 165). Match the tube. Nikon wants these used under fluorescent light rather than Choose color temperature (p. 174), which fits the physics: a tube's kelvin figure alone does not capture its colour.

Choose Color Temperature

Choose color temperature accepts any value from 2500 to 10,000 K (p. 165). With the buttons, hold Fn1 and turn the main command dial to select it, then keep holding and turn the sub-command dial (p. 172). From the menus, either photo or video, select it and press right. Left and right pick a digit, up and down change it, and the W (Q) button opens the fine-tuning grid (pp. 173-174). In the i menu, highlight it and press down (p. 175).

The number can come from a lamp's data sheet, a colour meter, or the camera itself. For pictures taken with Auto, Natural light auto or Preset manual, the Basic shooting data page in playback shows the colour temperature the camera used (p. 167). Tick Shooting data and Basic shooting data under Playback display options in the playback menu to see it. Shoot one frame on Auto, read the figure, dial it in, and every later frame is locked to it. The figure is not shown for high-speed frame capture + pictures (p. 167).

Preset Manual

Most presets and the Auto modes assume light reasonably close to a black body. A stage mixing tungsten front light with coloured LED side light breaks that assumption, and Nikon accepts that Auto, Incandescent and Choose color temperature may then fail (p. 176). Preset manual measures instead. You put something neutral in the light falling on the subject, and the camera computes the gains that make it neutral, exactly as in the grey-card sum above.

The camera stores up to six values, d-1 to d-6 (p. 176). Direct measurement runs through these actions in turn (pp. 176-178).

• Hold Fn1 and turn the main command dial to Preset manual, then, still holding, turn the sub-command dial to pick a slot.
• Let go of Fn1 briefly, then hold it down again, and the camera switches to direct measurement mode. The Preset manual icon flashes and a target appears mid-frame.
• Place the target over a white or grey object in the subject's light, using the multi selector or a tap on the monitor.
• Press the shutter-release button fully, or press OK, to measure. You may repeat this as often as you like.
• Press the i button to leave the mode.

With an optional flash unit attached the target cannot move, so centre the reference (p. 177). The mode ends when the standby timer in Custom Setting c3 runs out, and measurement is impossible during high-speed frame capture + or multiple exposure (p. 178). A reference that is too dark or too bright fails, and the camera shows a message and waits for another try (pp. 177, 916). A grey card made for the job is the best reference. Many printer papers contain optical brighteners, dyes that turn invisible ultraviolet into visible blue, so in daylight, which carries ultraviolet, such paper reads bluer than it looks, and correcting for it leaves the picture slightly warm.

You can also lift white balance from a picture on the card. Open White balance, highlight Preset manual and press right, highlight the slot to fill, and press the playback zoom-in button for the preset menu. Choose Select picture, highlight the source and press OK (pp. 179-180). Pictures from another type of camera cannot be used (p. 916). The same menu holds Fine-tune, Edit comment for a label of up to 36 characters, and Protect, which stops a preset being overwritten while set to ON (p. 180). Label stage presets with venue and date and protect them, so a stray press of Fn1 between acts cannot replace a good reading.

Fine-Tuning Amber, Blue, Green and Magenta

Every option can be nudged up to six steps either way along two axes: A (amber) to B (blue), and G (green) to M (magenta) (p. 168). The amber-blue axis follows colour temperature, is ruled in half steps, and one step is about 5 mired. The green-magenta axis acts like the colour compensation filters film users fitted to the lens, is ruled in quarter steps, and one step is about 0.05 diffuse density units (p. 168). Density is a logarithmic measure of how much light a filter holds back, and diffuse density is density measured with scattered rather than straight-through light. A density of 0.05 transmits $10^{-0.05} \approx 0.89$, about 89%, of the light in the band the filter absorbs, so each step is a gentle tint.

Six steps of 5 mired is about 30 mired either way. On Incandescent, at 333 mired, that spans roughly

$$\frac{10^6}{333 + 30} \approx 2750\ \text{K} \quad \text{to} \quad \frac{10^6}{333 - 30} \approx 3300\ \text{K},$$

while on Direct sunlight, at 192 mired, it spans about 4500 to 6200 K. My arithmetic, built on Nikon's figure, shows the range is roughly the same visual size on every preset even though its kelvin width differs threefold.

The axes are relative (p. 170). Pushing toward B on Incandescent makes the picture cooler than plain Incandescent, not blue. A fine-tuned setting puts an asterisk in the white balance icon (p. 168). To reach the grid, hold Fn1 and use the multi selector (p. 168), press right on an option in the menu (p. 169), or press down on it in the i menu for a live preview (p. 170). Two options differ. Choose color temperature shows its digits first, in the menu and the i menu alike, and the W (Q) button opens the grid from there (pp. 170, 173, 175). A Preset manual slot is fine-tuned through Fine-tune in its own preset menu (p. 180).

White Balance for Video

Left at Same as photo settings, video takes the stills setting (p. 589). Any other choice gives video its own value. Holding Fn1 and turning a command dial changes white balance during recording (p. 213), USB streaming uses the video-mode setting (p. 219), and AE/AWB lock (hold) is available as a video button role (p. 751). Video gets its own part later in this guide.

What the Display Shows

Custom Setting d10, View mode (photo Lv), decides whether the shooting display shows white balance at all. Show effects of settings does. Adjust for ease of viewing does not, and its Custom option can set a display white balance of its own (pp. 673-674). Video always shows the effects (p. 673). If you judge colour in the finder, keep d10 on Show effects of settings.

06.RAW Files Versus JPEG and HEIF

A NEF (RAW) file keeps the sensor's counts uncorrected, with your white balance recorded beside them. Converting it later, called NEF (RAW) processing, lets you change white balance freely while the RAW data stay untouched however often you process them (p. 118). The camera can do this itself. Press the i button during playback and open Retouch, where RAW processing (current picture) handles one frame and RAW processing (multiple pictures) a batch, with white balance among the adjustable settings and Original keeping the one you shot with (pp. 261-265). Nikon warns that hues from in-camera RAW processing may differ from the camera's own JPEG or HEIF even at identical settings (p. 261).

A JPEG or HEIF is finished at capture. The gains are applied, the Picture Control renders the look, and only the result is stored. You can still shift colour later, but on an image already rounded, tone-shaped and compressed, and a channel clipped by the original gains stays clipped.

So in RAW white balance is reversible, and in JPEG or HEIF it is final. It still matters in RAW, because it colours the shooting display and fixes the JPEG half of a RAW plus JPEG pair. It also explains why white balance bracketing, which saves several copies of each shot along the amber-blue axis, is unavailable whenever image quality includes NEF (RAW), alone or paired with a JPEG or HEIF (pp. 505-507, 916). Nikon gives no reason, but a RAW file holds the same counts whatever white balance is recorded beside them, so bracketed RAW copies would hold identical data. Formats are compared in RAW, JPEG, HEIF and Tone Mode, and the rendering after white balance belongs to Picture Controls and Colour.

07.Mixed Light at a Stage Show

Many dance stages mix tungsten front light, or white LEDs imitating tungsten, with followspots, which are often discharge lamps much nearer daylight, and with coloured LED washes from the sides and back. The grey-card sum sets the limit: one set of gains covers the frame, so you must decide which light defines white.

Choose the light on the faces, and if a followspot carries the dancer, measure the light where it falls on the dancer's face. An audience forgives a magenta backdrop and does not forgive green skin. Balance for the front light and the washes keep the colours the lighting designer chose. Do not neutralise a saturated wash: strongly coloured light sits far from the black-body colours, has no meaningful colour temperature, and correcting for it drags every skin tone the other way. A Preset manual measured in the front light also captures any green or magenta tint in white LED fixtures.

Auto struggles because the dominant colour changes from cue to cue, so its estimate can change too, and one sequence can come out in several slightly different colours. A fixed setting removes that, for the reason Nikon gives for time-lapse (p. 540).

08.Recommended Settings

Stage dance. With the Tamron 70-180mm f/2.8 at a recital, I would measure before the audience arrives. At a rehearsal, if allowed, hold a grey card in the white front light where the dancers stand, measure into d-1, comment it with venue and date, and protect it. If you cannot reach the stage, shoot one frame on Auto in plain white light, read Basic shooting data and dial the figure into Choose color temperature. I shoot RAW either way, because no setting suits every cue and batch correction is quick from a common starting value.

Golden-hour landscape. The orange of the low sun is the subject, and an automatic mode treats a cast as something to remove. Direct sunlight holds 5200 K, as if the scene were lit by midday sun, so the extra warmth stays. Cloudy or Shade adds more, since a higher setting gives a redder result (p. 167).

Portraits. With the Nikkor Z 85mm f/1.8 S in a studio or by a steady window, I would measure a Preset manual from a grey card at the face. In shifting daylight, Natural light auto follows the light within daylight values. With flash as the main light, use Flash, or Auto for its flash-aware behaviour.

Gimbal dance video. Give video its own fixed value, by Choose color temperature or a Preset manual measured on location. A move from a sunlit wall to a shaded one is the kind of change an automatic mode may follow, and a shift mid-clip is harder to hide than one between clips.

09.Beginner Mistakes

Correcting away the light you came for. Auto, and Keep white above all, treats warm light as a fault. At sunset or by candlelight, switch to Direct sunlight or Keep warm lighting colors.

Using Choose color temperature under tubes. Nikon says not to (p. 174). Use the matching Fluorescent preset or measure a Preset manual.

Neutralising coloured stage light. Balance for the white light on the faces and let the washes stay coloured.

Forgetting a fine-tune. A nudge toward amber made at sunset is still there next morning. Look for the asterisk and reset the grid when the job ends.

Measuring in the wrong light. A card in sun while the subject stands in shade measures the wrong light. Put it where the subject is, facing the same way.

10.Related Chapters

• RAW, JPEG, HEIF and Tone Mode: NEF (RAW), JPEG and HEIF, and why white balance stays editable only in RAW.
• Picture Controls and Colour: the colour and contrast rendering applied after white balance.
• Metering: how the camera judges brightness.
• Exposure Modes: the shooting modes, including the one that sets white balance for you.
• Menus and Controls: the i menu, Fn buttons and command dials.
• Glossary: colour temperature, mired, NEF (RAW) and RAW processing in brief.