Color and temperature

Learning goal

You will be able to explain why a photo comes out bright yellow, orange, ice blue or greenish. You will correct the shift between yellow and blue with the temperature slider and between green and magenta with the tint slider, base the correction not on your eye but on a white or gray object in the scene, decide in scenes with mixed lighting according to the side of the face that gets the main light, and at the end of the correction leave the skin of every tone with its own undertone, neither pale nor orange.

The question

At dinner, you photographed your family under a chandelier with yellow light. You are all laughing together at the table, and at that moment there is a warm, soft, sweet light. When you open the photo, though, everything is bright yellow: the white tablecloth is lemon yellow, the faces orange, the wall mustard-colored. The warmth you saw with your eyes is exaggerated in the photo as if a paint pot had been knocked over.

Why did my photo come out bright yellow? Because your brain is a machine that quietly corrects the color of light; a camera can't always manage this. In this lesson we will talk about how the color of light seeps into a photo, how to correct it with the temperature and tint sliders, and what you need to look at while correcting.

Context

In Lesson 5.1 you saw that light has a color and that our brain usually corrects this color without letting us notice: a sheet of paper looks white to our eye both next to a candle and at midday. A camera, on the other hand, makes this correction with a guess, and this is called white balance. Auto white balance usually does a good job, but it can get confused under warm bulbs, in dim cafés, on shaded streets and in rooms with mixed lighting.

In the workflow, color comes after light. The reason is simple: as brightness and contrast change, the way colors look changes a little too; adjusting the color after the light has settled gives a more reliable result. Whichever app you use, the two basic adjustments of the color step are found almost everywhere: one works between yellow and blue, the other between green and magenta. Their names can change by app, such as temperature, warmth, tint or hue.

Simple explanation

How does the color of light seep into a photo?

Every light source has a color, and this color is usually described by its color temperature, in a unit called the kelvin. Candlelight is around two thousand kelvins and orange. The warm white bulbs in homes are roughly between two thousand seven hundred and three thousand kelvins and yellow. Midday daylight is around five thousand five hundred kelvins and looks roughly white. Overcast weather and shade go up to six thousand five hundred kelvins and above and shift toward blue. The smaller the number, the warmer the light; the bigger, the cooler.

In auto white balance the camera guesses the color of the light in the scene and adds the opposite color to show white as white. In yellow light it adds a little blue; in blue shade, a little yellow. But if there is no white or gray surface in the scene, if the scene is already full of warm colors, or if the light is very warm, the guess can be wrong and the correction stays half done. The result is a bright yellow dinner or an ice-blue portrait in the shade. Kelvin alone doesn't describe the color fully: some lights shift off the yellow-blue axis, toward green or magenta.

What do the temperature and tint sliders do?

The temperature slider shifts the photo between yellow and blue. When you pull it one way the photo turns blue, the other way yellow. To correct a bright yellow evening photo you pull the slider toward blue; to correct an ice-blue portrait in shade, toward yellow. In RAW files this slider often shows a kelvin value; this value tells the camera in what color of light the photo was taken. Lowering the value means "the light was warm", and the app adds blue to the photo.

The tint slider, on the other hand, works between green and magenta. Some fluorescent lamps and cheap LEDs drop a greenish veil over a photo; in a portrait taken under leaves or in front of a green facade, a green reflection can fall on the face. Pulling the tint slider a little toward magenta wipes out this green. The other way round, in some night lights or in light reflected from screens, the photo shifts toward a pinkish magenta; then the slider is pulled toward green. In most photos temperature alone is enough, while tint is for fine-tuning.

What do you look at to correct it?

Your eye makes its own correction while you correct color too: after looking at a yellow photo for a few seconds, you notice the yellowness less. That is why you should correct color not by the feeling of your eye but by a reference. The best neutral reference is an object in the scene you know is white or gray: a tablecloth, a piece of paper, a T-shirt, a white wall, a plate. Adjust the sliders until that object looks neither yellow nor blue, neither green nor pink. Many apps also have an eyedropper tool; when you touch it to a white or gray surface, the app corrects the color itself.

Even once you have found a reference, the final decision is made by the feeling of the scene. When a candlelit dinner is made completely neutral, that warm atmosphere is lost; leaving a little warmth keeps the feeling of the moment. Pulling a city photo taken in the blue hour toward yellow wipes out the cool calm of that hour. The neutral reference shows you where the truth is; how far you move away from it you decide by looking at what the photo tells. What matters is choosing this shift knowingly, not giving in to the camera's mistake.

How do you keep skin tone?

Skin is the most sensitive place in color correction, because everyone knows how a person should look and notices a small deviation at once. But skin isn't a neutral reference: every skin comes with its own undertone; some are warm, golden or reddish, some cooler, olive or pinkish. That is why you should correct the color not by looking at the skin but by looking first at a white or gray object, and then check the skin. Trying to make skin "neutral" can make skin with a warm undertone look pale and ill.

In bright yellow light, dark skin shifts toward orange or copper, while light skin looks as if it has been coated with orange paint. In blue shade, dark skin shifts toward gray and ash, and light skin toward a purplish coldness. In mixed lighting, for example on a face lit blue from a window on one side and yellow from a lamp on the other, a single correction can't rescue both areas at once; then take the side where the face gets its main light as the reference, and accept the color difference left on the other side. If there are people of different skins in the same frame, look at each face separately at the end of the correction.

Visual evidence

You open the dinner photo under the chandelier. The white tablecloth is lemon yellow, the grandfather's dark brown skin has turned an orangey copper color, and your little sister's light skin an orange mask. The white paint on the wall is mustard-colored.

You have tidied up the light; now it is color's turn. You touch the eyedropper to a corner of the tablecloth that isn't in shadow; the tablecloth turns white, the wall off-white. But now the photo is a little too cold; the warmth of that evening seems lost. You pull the temperature slider back a little toward yellow; the tablecloth shifts to a slight cream color, and the light is warm again. Then you look at the faces: the grandfather's skin is in its own warm brown, with a slight redness on the cheeks; your sister's skin is pinkish and natural. You soften the greenish veil in the corner hit by fluorescent light leaking from the kitchen door by pulling the tint slider a little toward magenta. The same evening; this time the photo looks not painted, but lit.

Common mistakes

Summary

Every light has a color, and the camera's white balance can't always correct it; warm bulbs shift a photo toward yellow, shade toward blue, and some lamps toward green. The temperature slider corrects the shift between yellow and blue, and the tint slider between green and magenta. Adjusting the color not by the feeling of your eye but by a white or gray object, then deciding how much warmth to leave for the feeling of the scene, and checking separately whether every skin stays in its own undertone gives an honest color correction.

Mini assignment

Move on to the photos whose light you have tidied up and whose color has problems.

1. Choose at least three photos with shifted color: one taken in yellow light, one in shade or cloudy weather, one in mixed lighting.
2. In each one, find a white or gray object and make it neutral with the temperature slider or the eyedropper.
3. Look at whether neutralizing wiped out the feeling of the scene, and add back a little warmth or coolness if needed.
4. In every frame with people, note in one sentence whether each face looks its own undertone after the correction.

Check yourself

• Did you correct the color by the feeling of your eye, or by a reference?
• Were you able to tell apart a greenish or pinkish shift with the tint slider?
• After the correction, were dark and light skins freed from an orange, gray or purple veil?

Glossary

Mini quiz

1. Why can a photo taken under a yellow bulb come out bright yellow?

• A) Because the camera's white balance can't fully correct the color of the light
• B) Because the bulb is too bright
• C) Because the photo was cropped
• D) Because the contrast is too high

2. With which adjustment do you correct the greenish veil a fluorescent lamp drops on a photo?

• A) Brightness
• B) Pulling the temperature slider toward yellow
• C) Contrast
• D) Pulling the tint slider toward magenta

3. What is the most reliable reference when correcting color?

• A) The first feeling of your eye
• B) A white or gray object in the scene
• C) The brightest color in the photo
• D) A person's skin

4. What can happen if skin with a warm undertone is neutralized completely?

• A) The skin looks more natural
• B) The photo's sharpness increases
• C) The skin can look pale and ill
• D) The skin's color doesn't change, only the background does

Answers

1. A — The brain quietly corrects the color of light; the camera's white balance is a guess and can leave the correction half done in warm light.
2. D — The green-magenta axis is separate from the yellow-blue axis; the tint slider wipes out a green veil when pulled toward magenta.
3. B — The eye gets used to a color in a few seconds; an object known to be white or gray shows where the color really is.
4. C — Every skin comes with its own undertone; wiping out a warm undertone makes the skin look gray and lifeless, which is why skin isn't used as the reference.

Summary card

• Every light has a color: a candle orange, a bulb yellow, shade blue.
• Temperature: yellow and blue; tint: green and magenta.
• Correct not by your eye but by a white or gray object.
• After finding neutral, you can leave a little warmth for feeling.
• Skin isn't the reference; after correcting, look at each face's undertone.

Bridge to the next lesson

Now you can adjust cropping, light and color. Each of these tools strengthens a photo when used in moderation; but when pushed all the way, the photo turns into an oddly artificial image that "smells of filters". The next lesson talks about how this overdoing forms, where you need to stop the sliders, and the ways to stay natural.