photo laureates provides here tips on how to best use colors in photography.
The white balance setting of a camera relates exclusively to the colours that are captured. White balance is critical to a digital camera as it establishes the starting point for all the colours it will record. The purpose of white balance is to ensure that whatever the source of light, the colours of a subject photographed under that light will be reproduced as faithfully as possible.
By default, most digital camera's white balance systems rely on an Auto white balance , a series of algorithms that divide the image into many segments to evaluate the light source, and then compensate for it by shifting the colour spectrum of the image according to that light source. The light colour evaluation system works by comparing the data gathered against the known colour shifts imparted by different sources of light, such as sunlight, or fluorescent. Each camera manufacturer uses their own sets of algorithms to calculate the proper white balance for an image; and in most cases, the resulting colours are quite accurate. On occasion though, for a variety of reasons, the auto white balance can be in error, resulting in an image whose colours are not as accurate as they should be.
An incorrect white balance setting results in colour shifts, and these can be quite difficult to correct once the image has been finalized by the camera and saved in a format such as JPEG, or TIFF. This difficulty in correction, should the auto white balance be in error, is one of the advantages of the RAW image formats that are offered on some cameras. A RAW format allows correction to an improperly set white balance relatively easily, usually with the same software that is provided to convert the image into a more common format. On the other hand, correcting the white balance of images saved in other less flexible formats ¡ª JPEG for instance, which has deleted unnecessary colour information to reduce file size ¡ª is sometimes hopeless.
White light is composed of all colours, but white light, be it natural or artificial, can vary in its purity. We all know for instance that the light of the setting sun is much more red than the light of the sun at noon , and this is reflected in the way we see colours . Similarly, we can also tell that the light produced by a cool white fluorescent tube is a bit more green than the light produced by a standard incandescent bulb.
To demonstrate this, a series of images were taken using the Auto white balance of a camera, and switching the light sources for each shot.
In the still life shown here, the background is white, and can be used to see the impact of the light source.
 |
The first photo (at left) shows a correct white balance, and can serve to evaluate the others: |
 |
Auto white balance:
with incandescent light
(100W bulb) |
 |
Auto white balance:
with a Fluorescent Desk Lamp
(13 Watts U-shaped bulb) |
 |
Auto white balance:
with a cool white fluorescent
(12 Watts tube) |
As can be seen in the images above, the auto white is not always precise. Interestingly, with these examples, the auto white balance fares much better when the light source is the cool white fluorescent as that source of the light is more easily identifiable, something that appears to be the case with a number of cameras we tried.
Compensating for the light source
This next series of photos show the result of manually adjusting the white balance to the ambient light. Most cameras offer presets for common sources of light, and these generally provide good results. The same subject re-photographed, using the same light sources as were used above, but adjusting the camera's white balance to the preset offered for that specific light source :
 |
Light source: 100 Watt bulb
White balance Preset:
Incandescent or Tungsten |
As can be seen, using the Incandescent or Tungsten same concept setting for the white balance results in a correct image.
With the Desk Lamp Fluorescent light however, rectifying the colours proved to be much more complicated. Many cameras offer a variety of settings for different fluorescent lights, usually 3 settings, daylight fluorescent, warm white fluorescent, and cool white fluorescent. Each is tried in turn below:
 |
Light source: Fluorescent Desk Lamp
White balance preset:
Daylight Fluorescent |
 |
Light source: Fluorescent Desk Lamp
White balance preset:
Warm White Fluorescent |
 |
Light source: Fluorescent Desk Lamp
White balance preset:
Cool White Fluorescent |
As can be see above, none of these yield natural colours. In fact, the Fluorescent Desk Lamp tube seems to have a colour temperature that is closer to an incandescent bulb (below) . Although even then the result was not as good as it should be and the image retains a very noticeable yellow cast:
 |
Light source: Fluorescent Desk Lamp
White balance preset:
Incandescent/Tungsten |
When none of the preset white balance settings are perfect, the only option, if the camera is so equipped, is to set the white balance for that specific light source . That setting, referred to as a "user-set", or "spot white balance", is explained further on.
In this test, the problem experienced with the Fluorescent Desk Lamp does not occur with the standard cool white fluorescent. Setting the white balance to that specific preset yields an accurate image:
 |
Light source: Cool white fluorescent
White balance preset:
Cool White Fluorescent |
Colour Balance Outdoors
During the day, the sun is our primary source of light, but the colour of its light changes according to the time of day, and the weather. Generally, most Auto white balance systems are quite reliable under sunlight, be is direct or indirect, and setting the white balance to Sun or Daylight has very little impact. This can be seen in the examples below, both captured in direct sunlight:
Light source: direct sunlight
White balance set to Auto |
 |
Light source: direct sunlight
White balance set to Daylight/Sun |
 |
As these two photos show, whether the Auto white balance is used, or the Sun white balance preset, the results are similar. In fact, the Sun or Daylight presets offered on many cameras are best used only when the sun is directly overhead.
The Shade preset in most cameras is also designed for fine sunny weather, but is specifically intended for subjects that are not directly lit by the sun, a situation that makes colours bluer, and which this preset rectifies.
When the weather is cloudy, the Auto white balance may yield photos that have a pronounced bluish tint, particularly in shadow areas, and if a setting is available for Cloudy the image will generally show more faithful colours.
Setting the white balance for the ambient light
Many cameras offer at least one white balance setting that can be set to reflect the ambient light conditions. Most of these systems work by pointing the camera at a known white surface ¡ª under the ambient lighting of course so the white balance can use that as the white point. Note that for a few cameras, the user set white balance suggests the use of an 18% grey card . 18% grey cards can be purchased at specialty camera stores; often however, the settings can be done as well using a plain white surface.
To illustrate how user-set white balance works, we'll use the Fluorescent Desk Lamp example from above for which no setting was appropriate. To set the white balance for that specific light source, the camera is pointed at the white background which is also lit by that same light source so it fills the screen. Then the white balance is set.
As a reminder, the best match for the Fluorescent Desk Lamp within the white balance presets explored above, incandescent, is shown below at left. The image captured by the user-set white balance setting is shown at right:
 |
 |
Incandescent white balance setting |
User set white balance |
A proper white balance setting ensures that colours will be reproduced as faithfully as possible. And the best way to understand how any one camera reacts to different light sources, is to experiment with its options.
To learn more about light in photography, please visit this site and this site
|
