What is White Balance?
Ever wondered why your subjects turn out yellow when photographing them in indoor environments? Or why your camera flash can make them appear blue? Thoroughly understanding the concept of white balance and how it works is very important in digital photography, because setting it incorrectly could ruin a picture, adding all kinds of unwanted color casts and causing skin tones to look very unnatural. In this article, I will explain how you can adjust it on your camera or post-production to get accurate colors.
Definition of White Balance
Simply put, white balance in digital photography means adjusting colors so that the image looks more natural. We go through the process of adjusting colors to primarily get rid of color casts, in order to match the picture with what we saw when we took it. Why do we have to do this? Because most light sources (the sun, light bulbs, flashlights, etc) do not emit purely white color and have a certain “color temperature“. The human brain processes the information that comes from our eyes and automatically adjusts the color temperature, so we normally see the colors correctly. If you took a white sheet of paper and looked at it outside, it would most likely look as white as if you were to look at it indoors. What most people do not realize, however, is that there is a huge difference in color temperature between bright sunlight and indoors tungsten light.
If you are a skier or a snowboarder, try this quick experiment: put on your ski goggles and look at the snow – it should change in color tone. If you have ski goggles with a yellow tint, the snow will look yellowish. However, after you ski for a little bit, your eyes and your brain will adjust for the color and the snow should look white again. When you take off your ski goggles after skiing, the snow will look bluish in color rather than pure white for a little bit, until your brain adjusts the colors back to normal again. This example proves the fact that we are equipped with a very sophisticated color system that automatically adjusts colors in different lighting situations.
While our brains automatically process the colors for us in such a smart way, digital cameras can only guess what the color temperature is by watching the ambient light. In most cases, modern digital cameras can guess pretty well, however, in some situations they make errors. Because of these errors, some of the pictures might appear to be bluish or yellowish in color and the skin tones might not look natural.
Here is an example of both correct and incorrect White Balance:
Color temperature describes the spectrum of light which is radiated from a “blackbody” with that surface temperature. A blackbody is an object which absorbs all incident light — neither reflecting it nor allowing it to pass through. A rough analogue of blackbody radiation in our day to day experience might be in heating a metal or stone: these are said to become “red hot” when they attain one temperature, and then “white hot” for even higher temperatures. Similarly, blackbodies at different temperatures also have varying color temperatures of “white light.” Despite its name, light which may appear white does not necessarily contain an even distribution of colors across the visible spectrum:
Relative intensity has been normalized for each temperature (in Kelvins).
Note how 5000 K produces roughly neutral light, whereas 3000 K and 9000 K produce light spectrums which shift to contain more orange and blue wavelengths, respectively. As the color temperature rises, the color distribution becomes cooler. This may not seem intuitive, but results from the fact that shorter wavelengths contain light of higher energy.
Why is color temperature a useful description of light for photographers, if they never deal with true blackbodies? Fortunately, light sources such as daylight and tungsten bulbs closely mimic the distribution of light created by blackbodies, although others such as fluorescent and most commercial lighting depart from blackbodies significantly. Since photographers never use the term color temperature to refer to a true blackbody light source, the term is implied to be a “correlated color temperature” with a similarly colored blackbody. The following table is a rule-of-thumb guide to the correlated color temperature of some common light sources:
|Color Temperature||Light Source|
|2500-3500 K||Tungsten Bulb (household variety)|
|3000-4000 K||Sunrise/Sunset (clear sky)|
|4000-5000 K||Fluorescent Lamps|
|5000-5500 K||Electronic Flash|
|5000-6500 K||Daylight with Clear Sky (sun overhead)|
|6500-8000 K||Moderately Overcast Sky|
|9000-10000 K||Shade or Heavily Overcast Sky|
In Camera White Balance
Most cameras come with the option to manually set or adjust white balance. Typical settings include “sun”, “shade”, “tungsten” and “fluorescent”. Some cameras come with the option to manually set a color temperature by choosing a specific Kelvin value.
Let’s take a look at a few examples:
In the image on the left, you can see how orange the light bulbs look when the camera is set to a neutral white balance, but once it is changed to the color temperature of the bulbs (either manually or with a preset white balance), they look normal. Why is that? The camera is “cooling” down the color temperature of the bulbs by adding blue to the photo, giving us the appearance of white light. Notice that while the light bulbs now look white, the bokeh in the background now looks blue.
Let’s take one more example. Take a look at these images of the same scene that were taken in daylight:
Now that it’s daylight, you can see that 5500 K is the correct white balance for the color temperature. What happens if white balance is set to 3050 K in daylight? The image turns blue! This is how much blue was added to the photo of the orange incandescent bulbs to balance the orange and make the color temperature of the incandescent light look normal.
Post Processing White Balance
If you don’t want to worry about changing the white balance in your camera for different situations, as long as you’re shooting RAW you can always adjust the white balance of your images with post processing software such as Adobe Photoshop or Lightroom. This is sometimes referred to as “color correction”. In your software you’ll probably see a panel that looks something like this:
Just like setting the white balance in your camera, you can manually set the white balance either by adjusting the temperature value or by using the eyedropper tool on the left side and clicking on a neutral or white part of the image. Similar to your camera, you can also choose a preset white balance:
Here is the same image from above, both straight out of camera and with the white balance adjusted in Lightroom. Compare it to the image where white balance adjustment was done in camera:
Remember, this is only possible if you are shooting RAW images. If you are shooting JPEG, you will be able to make slight white balance adjustments to your images but will not be able to make drastic corrections.
Here’s another example of adjusting white balance in post processing. This photo was taken during an engagement session that started in daylight, so the camera is set to a white balance of 5500 K. As the sun started to set, the light got warmer and warmer, giving this image a very orange feel.
Now some people might like a sunset image to be this warm (it personally doesn’t bother me that much), but it needed cooled down a bit to really bring out the pinks and blues in the sky, not to mention make their skin look a bit more normal. In Lightroom, the white balance was adjusted so that the temperature was at 4500 K, giving this image which looks more natural:
The Relation Between Color Temperature and White Balance
Now that you know the difference between color temperature and white balance, you should be able to see the relationship between them. They are opposites! Unfortunately, since photographers mainly work with white balance, we sometimes get confused when referring to color temperature values.
It is recommended to almost always shoot at a fixed Kelvin of around 5500 K. When photographing interiors that are lit by incandescent bulbs, all images look orange. If you shoot RAW, it’s not a problem! In Lightroom you can just “cool them off” by changing your white balance to around 3000 K. For shade, you “warm up” your shady images by changing the white balance to around 6500 K. Higher Kelvin values start to equate to warm light and lower Kelvin values start to equate to cool light.
But remember to balance the color temperature! What you actually do is add the opposite color temperature to your image to make it look natural.
So now for the big conclusion you can draw from all of this. If you set your white balance to the color temperature of the scene you’re photographing, it should look great! If you’re photographing light bulbs that have a color temperature of 3000 K and you set your camera’s white balance to 3000 K, the light should look white! Now here’s the bad part. There’s really no way to measure color temperature, so you’re left approximating or adjusting in post processing.
Preset White Balance Settings
Auto – The Auto setting helps in adjusting the white balance automatically according to the different lighting conditions, but you can try other modes to get better results.
Tungsten – This mode is used for light under a little bulb like tungsten, and it is often used while shooting indoors. The tungsten setting of the digital camera cools down the color temperature in photos.
Fluorescent – This mode is used for getting brighter and warmer shots while compensating for cool shade of fluorescent light.
Daylight – This mode is for the normal day light setting, while shooting outdoors. Many cameras do not have the Daylight mode.
Cloudy – This mode is ideal for while shooting on a cloudy day. This is because it warms up the subject and surroundings and allows you to capture better shots.
Flash – The flash mode is required when there is inadequate lighting available. This mode helps pick the right White Balance under low light conditions.
Shade – A shaded location generally produces cooler or bluer pictures, hence you need to warm up the surroundings while shooting shaded objects.
Using Auto White Balance
If you prefer shooting JPEG or just don’t want to worry about color correction after the image is taken, most (if not all) cameras and post processing software come with the option to use auto white balance, or AWB. With AWB, your camera evaluates the scene that you’re photographing and decides on the best white balance to use. It will typically reference a neutral color in your scene such as white or grey to determine the correct white balance. Depending on your camera and the scene you’re photographing, your results will range from perfect to not very close at all.
Using Auto White Balance In Camera
When using auto white balance in camera, your results will vary depending on the lighting conditions you’re shooting in. For example, if you’re shooting in daylight the white balance of your photos will typically look correct. Unfortunately, mixed lighting can really give AWB troubles, so you might still end up needing to adjust the white balance in post processing.
Even daylight can fool auto white balance. Here’s a set of images of an orange fox on a brown table that really demonstrate how inconsistent auto white balance can be without a neutral color in the image for your camera to reference:
All of these images were photographed in the same light. You can see how much of a difference the background makes when using auto white balance. In the third image, simply adding a white background helped the camera get the correct white balance. You can see the last image is the same as the 2nd image, only with a correct white balance (adjusted in Lightroom).
Different cameras have different auto white balance capabilities. As with any technology, more recent cameras seem to be more accurate than older cameras. You’ll also typically have more advanced capabilities in more expensive cameras. That’s not to say that the AWB systems in entry level cameras are not good. For example, an iPhone 6 does a good job with AWB, but chances are a Nikon D810 does a better job getting it right more consistently.
Using Auto White Balance In Post Processing
Most, if not all post processing software such as Adobe Photoshop or Lightroom comes with an auto white balance option. This is never as accurate as shooting with AWB in camera, but it can serve as a good starting point if you’re trying to adjust the white balance in your image and just can’t seem to get it right.
Here’s an example of using auto white balance in Lightroom on a simple, sunlit photo:
CUSTOM WHITE BALANCE: CHOOSING A NEUTRAL REFERENCE
A neutral reference is often used for color-critical projects, or for situations where one anticipates auto white balance will encounter problems. Neutral references can either be parts of your scene (if you’re lucky), or can be a portable item which you carry with you. Below is an example of a fortunate reference in an otherwise bluish twilight scene.
On the other hand, pre-made portable references are almost always more accurate since one can easily be tricked into thinking an object is neutral when it is not. Portable references can be expensive and specifically designed for photography, or may include less expensive household items. An ideal gray reference is one which reflects all colors in the spectrum equally, and can consistently do so under a broad range of color temperatures. An example of a pre-made gray reference is shown below:
Common household neutral references are the underside of a lid to a coffee or pringles container. These are both inexpensive and reasonably accurate, although custom-made photographic references are the best (such as the cards shown above). Custom-made devices can be used to measure either the incident or reflected color temperature of the illuminant. Most neutral references measure reflected light, whereas a device such as a white balance meter or an “ExpoDisc” can measure incident light (and can theoretically be more accurate).
Care should be taken when using a neutral reference with high image noise, since clicking on a seemingly gray region may actually select a colorful pixel caused by color noise:
In addition to color temperature, light can also have a tint. While color temperature ranges within the orange/blue spectrum, tint ranges within the green/magenta spectrum. Major tint adjustments are typically not necessary when color correcting images taken in daylight. If you tend to photograph subjects that are lit by artificial light sources such as tungsten, fluorescent, LED or mercury vapor lights, you’ll find yourself adjusting tint much more than with natural light.
Here’s an example of a scene that was lit by fluorescent lights:
You can see that the first image has a very strong green tint. By changing the tint (adding magenta) but leaving the color temperature untouched, the white balance has been corrected.
Tint is not meant to compensate for color that is reflected onto your subject from nearby objects, such as in this image:
Melissa was facing a green door specifically to demonstrate this scenario. Although the white balance of in the image is correct, there is a green tint to the shadow side of her face that has nothing to do with color temperature. It is a reflection of light off of the green door and can not be corrected by adjusting the tint of the image.
Just like reflected light that has picked up a color cast, colored or gelled lights on your subject are also not easily corrected by adjusting the tint of your image. For example, this image from a New Year’s Eve wedding has everything you’d want in an image taken at the stroke of midnight: streamers, celebrating, happy green faces on the bride and groom… wait, what?
Unfortunately, this is not something that can be fixed by adjusting the white balance. Fortunately, it still looks pretty good in black and white.
IN MIXED LIGHTING
Multiple illuminants with different color temperatures can further complicate performing a white balance. Some lighting situations may not even have a truly “correct” white balance, and will depend upon where color accuracy is most important.
|Reference : Moon, Stone|
Under mixed lighting, auto white balance usually calculates an average color temperature for the entire scene, and then uses this as the white balance. This approach is usually acceptable, however auto white balance tends to exaggerate the difference in color temperature for each light source, as compared with what we perceive with our eyes.
Exaggerated differences in color temperature are often most apparent with mixed indoor and natural lighting. Critical images may even require a different white balance for each lighting region. On the other hand, some may prefer to leave the color temperatures as is.
Note how the building to the left is quite warm, whereas the sky is somewhat cool. This is because the white balance was set based on the moonlight — bringing out the warm color temperature of the artificial lighting below. White balancing based on the natural light often yields a more realistic photograph. Choose “stone” as the white balance reference and see how the sky becomes unrealistically blue.
As long as you shoot in RAW, knowing the color temperature of different light sources is not that important. Simply understanding the basic concept of color temperature should be enough for most photographers. What is important is knowing how and when to adjust white balance, either in camera before you create an image or in post processing software after you create an image.
Once you get comfortable adjusting the white balance of your images, you can start to use white balance creatively in your images, either warming them up or cooling them down to change the feel of the entire scene. Although that’s not something we’re going to go into for now, keep an eye out for a future article on creative use of white balance.