White Balance and The Colour of Light

A photo demonstrating different white balance and colour of light on a grocery store sign.

Have you ever tak­en a pic­ture and dis­cov­ered that your sub­ject appeared too orange or blue? Then you’ve encoun­tered a sit­u­a­tion where your camera’s white bal­ance was set incor­rect­ly for the scene.

Colour of light

All sources of light (“illu­mi­nants”) have colour. The colour of the light influ­ences our per­cep­tion of the colour of objects. Some illu­mi­nants, such as neon light tubes, emit light with­in a very nar­row band of the vis­i­ble spec­trum. This type of coloured light is very sat­u­rat­ed, and neu­tral-coloured objects illu­mi­nat­ed by it will take on its hue.

When a source emits light con­tin­u­ous­ly across the vis­i­ble spec­trum or in dis­crete and even­ly spaced bands, it’s con­sid­ered “white light.” Although white light exists in var­i­ous shades, its defin­ing char­ac­ter­is­tic is that it pro­vides a rea­son­able ren­di­tion of the colour of objects. For exam­ple, the sun appears white because it emits light almost even­ly across the vis­i­ble spec­trum. Rel­a­tive to sun­light, incan­des­cent light­bulbs (those with tung­sten fil­a­ments) look amber-yel­low because they emit a more sig­nif­i­cant por­tion of their light in the orange-red rather than the vio­let-blue part of the vis­i­ble spec­trum. Under both types of white light, red-coloured objects will appear red, green-coloured objects will appear green, and so forth. 

When tran­si­tion­ing between dif­fer­ent sources of light, our eyes are remark­ably adept at adjust­ing to vari­a­tions in white light so that neu­tral-coloured objects, such as white sheets of paper, are per­ceived as white under both sun­light and lamp­light. How­ev­er, unlike our eyes, cam­eras see colour as absolute and can­not adapt to the pre­vail­ing tone of the light, and this can result in auto white bal­ance errors.

Colour Temperature

Colour temperature

In pho­tog­ra­phy, colour tem­per­a­ture describes the rel­a­tive warm or cool appear­ance of white light. Cam­eras let you select a colour tem­per­a­ture in Kelvins. On many cam­eras, this scale ranges from about 2500 to 10,000 K, with the low­er ranges rep­re­sent­ing orange-amber sources, such as incan­des­cent bulbs, and the high­er ranges rep­re­sent­ing bluish-white sources, such as light from the blue sky (“sky light”). Actu­al day­light, being direct over­head sun­light with a clear sky, is rep­re­sent­ed by approx­i­mate­ly 5600 K. This close­ly cor­re­sponds to the out­put colour tem­per­a­ture of most elec­tron­ic flash­es and the ide­al colour of light for most con­sumer pho­to­graph­ic film.

Colour temperature and black body radiation

Why is the SI unit of tem­per­a­ture, the Kelvin, used to describe the warm or cool appear­ance of light in pho­tog­ra­phy? Colour tem­per­a­ture rep­re­sents the spec­tral dis­tri­b­u­tion of light emit­ted by an ide­al­ized “black body” with that sur­face tem­per­a­ture. A black body is a sol­id object that is opaque and non-reflec­tive. All solids above 0 K emit elec­tro­mag­net­ic radi­a­tion. As the tem­per­a­ture of a sol­id object increas­es, so too does its radia­tive ener­gy. This radia­tive ener­gy cross­es into the vis­i­ble spec­trum as a dim red­dish glow when the tem­per­a­ture of the sol­id ris­es to about 798 K. Assum­ing its tem­per­a­ture could grow indef­i­nite­ly, the vis­i­ble light it emits would tran­si­tion from red­dish-orange to yel­low to white and, final­ly, to bluish-white. Of course, most met­als will melt before achiev­ing a yel­low-ish glow. Tung­sten is an excep­tion. The thin tung­sten fil­a­ments used in reg­u­lar incan­des­cent light­bulbs reach tem­per­a­tures (and colour tem­per­a­tures) of approx­i­mate­ly 2750 K and can go up to 3200 K in halo­gen enclo­sures.

We use the term cor­re­lat­ed colour tem­per­a­ture to describe the appar­ent colour qual­i­ty of white light that cor­re­sponds to the colour tem­per­a­ture of a black body source. For exam­ple, the com­mon­ly accept­ed cor­re­lat­ed colour tem­per­a­ture of an over­cast sky, which at 6500–8000 K is slight­ly cool­er than day­light, is not indica­tive of its actu­al tem­per­a­ture. Sim­i­lar­ly, mod­ern LEDs, flu­o­res­cent tubes, and CFLs can evoke the appar­ent colour qual­i­ty of warm incan­des­cent or cool day­light sources of light with­out the cor­re­spond­ing tem­per­a­tures.

Colour temperature in practice

When your camera’s colour tem­per­a­ture set­ting match­es the colour tem­per­a­ture of the illu­mi­nant, your white bal­ance is neu­tral. When your camera’s colour tem­per­a­ture is set high­er than the colour tem­per­a­ture of the illu­mi­nant, your pic­ture will appear warmer. When your camera’s colour tem­per­a­ture is set low­er than the colour tem­per­a­ture of the illu­mi­nant, your pho­to will look more blue-ish.

For exam­ple, if your camera’s white bal­ance is set to match day­light and you’re tak­ing pic­tures illu­mi­nat­ed pre­dom­i­nant­ly by incan­des­cent light­ing, your pho­to will have a sig­nif­i­cant amber-orange colour cast. How­ev­er, if your camera’s white bal­ance is set to match incan­des­cent light and you’re tak­ing pic­tures under day­light con­di­tions, your pho­to will have a sig­nif­i­cant blue colour cast.

Media

Available light portrait of elderly lady cool white balance
This por­trait looks too cool in tone. The cam­era was bal­anced to day­light and the pri­ma­ry source of light was sky light from a large win­dow, which has a cool­er cor­re­lat­ed colour tem­per­a­ture.
Available light portrait of elderly lady white balance
This ren­di­tion of the por­trait is bal­anced for the sky light from the win­dow. The subject’s skin tone appears warmer and more pleas­ing. The camera’s white bal­ance is set to cor­rect­ly match the main illu­mi­nant.

Colour Tint

Colour tint

Colour tint describes the pres­ence of a green or magen­ta colour cast in white light. An illu­mi­nant can exhib­it one or the oth­er, but nev­er both, as they can­cel one anoth­er. Such colour casts are gen­er­al­ly con­sid­ered unde­sir­able in pho­tog­ra­phy. Por­traits with a green colour cast give their sub­jects a sal­low, unhealthy com­plex­ion, where­as magen­ta colour casts pro­duce com­plex­ions that appear too rud­dy and rubescent.

The pres­ence of colour tint is often seen when tak­ing pho­tos under arti­fi­cial illu­mi­nants that have dis­crete, non-con­tin­u­ous emis­sions across the vis­i­ble spec­trum of light. These include many con­sumer LEDs, flu­o­res­cent tubes and CFLs, street lamps, etc. Colour tint is rarely encoun­tered when tak­ing pho­tos under nat­ur­al sources of light (day­light, over­cast, sky­light), incan­des­cent light, or xenon flash.

 

Media

Taipei street food stalls with green tint white balance.
In this pho­to­graph, the flu­o­res­cent lamps cast a green-tint­ed light onto the scene.
Taipei street food stalls with colour tint white balance.
In this ren­di­tion of the pre­vi­ous pho­to, the colour tem­per­a­ture remains the same while the flu­o­res­cent green tint has been neu­tral­ized.

What is White Balance

White balance

White bal­ance (WB) is a com­pu­ta­tion­al process for remov­ing colour casts from your images so that sub­jects that are colour-neu­tral in real­i­ty are ren­dered neu­tral in the result­ing pho­to­graph. It’s accom­plished by match­ing the inter­pre­ta­tion of record­ed colours to the colour of light pro­duced by the illu­mi­nant. In dig­i­tal pho­tog­ra­phy, white bal­ance is achieved entire­ly through soft­ware manip­u­la­tion of the image. Adjust­ing the white bal­ance set­ting doesn’t affect your expo­sure para­me­ters or any oth­er phys­i­cal char­ac­ter­is­tic of the cam­era or lens.

When your camera’s white bal­ance is set to match the dis­tinc­tive colour of a giv­en illu­mi­nant, your white bal­ance is con­sid­ered accu­rate. For exam­ple, if you’re tak­ing a pic­ture under mid­day sun­light and set your camera’s white bal­ance to day­light, your white bal­ance is cor­rect because your camera’s inter­pre­ta­tion of colours will match the prin­ci­pal light source; whites and greys, in real­i­ty, will appear white and grey in the result­ing pic­ture. How­ev­er, if you set your camera’s white bal­ance to day­light and you take a pho­to of a sub­ject under incan­des­cent light, your white bal­ance set­ting would be incor­rect because your camera’s inter­pre­ta­tion of colours will not match the pre­vail­ing illu­mi­nant; whites and greys will appear amber in the result­ing pho­to­graph.

Auto white balance

Auto white bal­ance (AWB) is the default set­ting on new cam­eras and in the auto­mat­ic shoot­ing modes. When auto white bal­ance is engaged, the cam­era reads the scene and attempts to deter­mine the colour tem­per­a­ture and tint of the light based on fac­tors such as pro­grammed adjust­ments, the over­all bal­ance and dis­tri­b­u­tion of hues and tones in the com­po­si­tion, and the pres­ence of skin tones when aid­ed by face detec­tion (where avail­able).

Auto white bal­ance gen­er­al­ly pro­vides excel­lent results for scenes that con­tain a promi­nent neu­tral-coloured object, a suit­able vari­ety and dis­tri­b­u­tion of colours, and when pho­tographed under a sin­gle source of aver­age out­door light.

Auto white bal­ance tends to err in scenes that lack a neu­tral-coloured ref­er­ence object and have an over­abun­dance of warm or cold tones or green or magen­ta hues in the sub­ject mat­ter. For exam­ple, when tak­ing a full-body por­trait against a back­ground of lush green veg­e­ta­tion, the cam­era can mis­take the pres­ence of green-coloured objects for a pro­fu­sion of green-tint­ed light. [Cam­eras can­not rea­son like peo­ple and don’t have a basic under­stand­ing of the scene and its sub­jects; they’re inca­pable of dif­fer­en­ti­at­ing between green objects lit by day­light and grey objects illu­mi­nat­ed by green light.]. It will attempt to fix this by bring­ing the aver­age colour of the scene clos­er to neu­tral by adding magen­ta, which is com­ple­men­tary to green. This solu­tion will desat­u­rate the greens and add a magen­ta cast to the remain­ing colours.

 

Preset White Balance

White balance presets

Many cam­eras let you man­u­al­ly select from among sev­er­al gen­er­al white bal­ance pre­sets designed for sit­u­a­tions where you antic­i­pate that auto white bal­ance will encounter prob­lems, such as scenes dom­i­nat­ed by mono­chro­mat­ic sub­jects. The fol­low­ing overview describes each pre­set and the gen­er­al con­di­tions for which they’re pre­scribed. Your cam­era will not nec­es­sar­i­ly have every pre­set.

Shade. This white bal­ance pre­set is meant for use in the day­time in rel­a­tive­ly cloud­less to part­ly cloudy con­di­tions when your sub­ject is shad­ed from direct sun­light and illu­mi­nat­ed almost exclu­sive­ly by sky light. It bal­ances the camera’s inter­pre­ta­tion of colour for the sig­nif­i­cant pres­ence of blue-ish white light.

Cloudy. This white bal­ance pre­set is meant for use dur­ing day­time and under heavy cloud cov­er or over­cast con­di­tions. It can also be the right choice when the day­light set­ting pro­duces cool­er than expect­ed results, such as at high ele­va­tions or in hazy con­di­tions.

Day­light. This pre­set is intend­ed to match the colour tem­per­a­ture of direct mid­day sun­light under a clear or part­ly cloudy sky. The pre­cise colour tem­per­a­ture of this set­ting varies among cam­eras, falling into the range of 5000–5500 K. [The colour tem­per­a­ture of sun­light changes through­out the day and espe­cial­ly when the sun is near the hori­zon. There­fore, the day­light white bal­ance pre­set will not give per­fect­ly neu­tral results at all times. See What is a “cor­rect” white bal­ance?]

Flash. The xenon flash­es found in most cam­eras and hot-shoe-mount­ed speed­lights are designed to close­ly resem­ble the spec­tral qual­i­ty and colour of direct sun­light, which is about 5600 K. This can vary by a few hun­dred kelvins between brands. When a flash is used to take a pho­to indoors at night with ambi­ent incan­des­cent light­ing, your white bal­ance should be set to flash. This will give you a neu­tral ren­di­tion of your pri­ma­ry sub­jects with an amber-coloured back­ground.

Flu­o­res­cent. The flu­o­res­cent white bal­ance pre­set is designed to min­i­mize the green colour cast pro­duced by flu­o­res­cent tubes, CFLs, sodi­um- and mer­cury-vapour, and met­al halide light­ing fix­tures. Some cam­eras have a sin­gle flu­o­res­cent pre­set while oth­ers have sev­er­al because flu­o­res­cent lights (much like LEDs, to which this pre­set is also applic­a­ble) are avail­able in many varieties—from warm-white to cool-white light—and with vary­ing degrees of a green cast—from none to lots. Because of these unpre­dictable, try using Auto white bal­ance or set up a Cus­tom white bal­ance (See below Cus­tom) when you find that your cam­era doesn’t have an ade­quate pre­set for the flu­o­res­cent light you are try­ing to match.

Tung­sten or Incan­des­cent. The tung­sten or incan­des­cent white bal­ance pre­set on most cam­eras is intend­ed for tak­ing pho­tos of sub­jects illu­mi­nat­ed by true tung­sten fil­a­ment light­bulbs that emit a con­tin­u­ous spec­trum of light with colour tem­per­a­tures between 2750 K (con­ven­tion­al 60 W bulb) and 3200 K (halo­gen bulbs, like in pot lights). This pre­set is also appro­pri­ate for high-qual­i­ty warm-white LED lamps that have no or very min­i­mal green colour casts.

K. The K or Kelvin white bal­ance set­ting allows you to man­u­al­ly select a colour tem­per­a­ture val­ue with­in a pre­de­fined range, which is typ­i­cal­ly 2500-10,000 K.

Cus­tom. With the cus­tom white bal­ance set­ting, you pre­cise­ly set the white bal­ance to match the colour of the illu­mi­nant by using a neu­tral ref­er­ence tar­get. This works by choos­ing a neu­tral sub­ject as a point of ref­er­ence and tak­ing a pho­to of it under the source of light to which you match the cam­era. The cam­era ana­lyzes the ref­er­ence pho­to and deter­mines a white bal­ance that pre­cise­ly match­es the light con­di­tions. The pro­ce­dure varies sig­nif­i­cant­ly across dif­fer­ent makes and mod­els: refer to your camera’s instruc­tion man­u­al for spe­cif­ic direc­tions.

White balance: JPEG and raw

Your camera’s white bal­anc­ing process is entire­ly dig­i­tal and manip­u­lates the data after the pho­to­graph is cap­tured. Fur­ther­more, recall that raw images con­tain unprocessed data and that JPEG images are derived from raw data that’s been processed by the cam­era, and that white bal­ance is a nec­es­sary step in that process. There­fore, select­ing the right white bal­ance is essen­tial when sav­ing JPEG images because your choice becomes an inher­ent part of the pho­to­graph, and any attempt to cor­rect it after­wards will neg­a­tive­ly affect image qual­i­ty. Con­verse­ly, raw images are entire­ly unaf­fect­ed by your choice of white bal­ance. You may mod­i­fy the white bal­ance of a raw image dur­ing the edit­ing process with­out degrad­ing its qual­i­ty.

 

Godzilla toy in craft shop showing incorrect white balance
For this pho­to­graph, the cam­era was mis­tak­en­ly left in day­light white bal­ance, yet the scene was illu­mi­nat­ed by cool flu­o­res­cent light­ing with a strong green cast.

Media

Godzilla toy in craft shop showing JPEG file whose white balance was corrected.
The white bal­ance of the JPEG ver­sion of the pho­to was adjust­ed using the white area high­light­ed by the red square (bot­tom right). Note the amount of yellow/green cast still present through­out the image.
Godzilla toy in craft shop showing raw file whose white balance was corrected.
The white bal­ance of the raw for­mat pho­to was adjust­ed using the white area high­light­ed by the red square (bot­tom right). The per­vad­ing yel­low­ish-green cast is com­plete­ly neu­tral­ized through­out because the raw for­mat image con­tains much more data and colour infor­ma­tion than the JPEG ver­sion.

Mixed Sources of Light

Balancing mixed sources of coloured light

There will be occa­sions where you’ll encounter mul­ti­ple illu­mi­nants with dif­fer­ent colour tem­per­a­tures, tints, or both. There’s no sin­gle rule of thumb for cor­rect­ly han­dling such sit­u­a­tions, although there are sev­er­al approach­es that deserve your con­sid­er­a­tion. First, if you’re in a hur­ry or the pic­ture is fleet­ing, take the pho­to in raw for­mat. This approach will allow you to post­pone a deci­sion until a lat­er time.

Sec­ond, des­ig­nate one of the illu­mi­nants as your “key-light” and set your white bal­ance to match it. In pho­tog­ra­phy, the key light is the main illu­mi­nant for your sub­ject. For exam­ple, if you’re set­ting up an inte­ri­or por­trait, and your sub­ject is illu­mi­nat­ed part­ly by lamp­light (from inside) and part­ly by day­light (through a win­dow), set your white bal­ance to match the illu­mi­nant pro­vid­ing light to the most visu­al­ly promi­nent part of their face.

Third, when there is no appar­ent key-light, set the white bal­ance to match with either the nat­ur­al light (if avail­able) or the coolest ambi­ent illu­mi­nant. In gen­er­al, mixed-light images are more pleas­ing when the warm-coloured ele­ments are ren­dered warmer than we remem­ber than when cool-coloured details are made cool­er than we remem­ber.

 

Media

Quebec City at twilight daylight white balance.
This day­light white bal­ance rep­re­sen­ta­tion of Que­bec City at Twi­light appears very pleas­ing because it bal­ances the colour of the sky and allows the street and build­ing lamps to take on a warm tone.
Quebec City at twilight incandescent white balance.
This pho­to of Que­bec City at twi­light is white bal­anced more close­ly with the street and build­ing lights. How­ev­er, since they illu­mi­nate a rel­a­tive­ly small por­tion of the scene, the cityscape takes on a very blue appear­ance.
White balancing a mixed light portrait.
When tak­ing por­traits in scenes with mixed light, it’s typ­i­cal­ly ide­al to bal­ance the whites against the illu­mi­nant that fea­tures most promi­nent­ly on your sub­ject. In this pho­to, the camera’s white bal­ance was set to match with the key-light illu­mi­nat­ing the cen­tral por­tion of the subject’s face.

Correct White Balance

What is “correct” white balance?

Up to this point, we’ve described the con­cept of white bal­ance in absolute terms: it’s cor­rect­ly set when a neu­tral object, in real­i­ty, is ren­dered neu­tral in the result­ing pic­ture. Despite this, you will encounter sit­u­a­tions where a neu­tral ren­di­tion of neu­tral sub­jects will pro­duce less pleas­ing pho­tographs than those exhibit­ing a colour cast. For exam­ple, the colour tem­per­a­ture of the set­ting sun is sim­i­lar to that of an incan­des­cent light­bulb and becomes pro­gres­sive­ly red­der as it dis­ap­pears beyond the hori­zon. This gold­en-orange light is high­ly sought after by pho­tog­ra­phers, and for a good reason—it’s uni­ver­sal­ly appeal­ing. Set­ting your camera’s white bal­ance to match the colour tem­per­a­ture of the set­ting sun cre­ates a visu­al dis­so­nance between the pho­to­graph and your rec­ol­lec­tion of the scene. Sim­i­lar­ly, the colour of light from camp­fires, fire­places, and can­dles is often ren­dered much warmer than neu­tral.

Beyond per­mit­ting spe­cif­ic sources of light to fall in line with your visu­al mem­o­ry of the scene, your choice of white bal­ance can rely entire­ly on aes­thet­ic con­sid­er­a­tions. You may choose to ren­der a rainy scene as cool­er than neu­tral to empha­size the weath­er, or warmer than neu­tral to dimin­ish it. Ulti­mate­ly, the choice rests on your aes­thet­ic pref­er­ences.

Media

Toronto Riverdale Park East sunset warm white balance
With the white bal­ance delib­er­ate­ly set to day­light (5500 K), the warm light of the set­ting sun sat­u­rates the scene.
Toronto Riverdale Park East sunset cool white balance
With the white bal­ance delib­er­ate­ly set to match the set­ting sun­light (about 3000 K), the scene appears over­whelm­ing­ly cold.

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