Correct White Balance Gives the Right Colors
Why are images sometimes a bit too yellow or blue in tone? Well, the light around us has different color. The eye and the brain adapts to it while the camera has a bit more "objective" approach to the color of the light. We may therefore have to help the camera to interpret the color of the light in a manner more in tune with our subjective experience.
If we are in a white room that is illuminated by a yellowish incandescent light, we after a while perceive the walls as more or less white. But a camera records exactly what it sees, and the result would be quite a yellowish image, although the camera in its automatic white balance mode, tries to measure color of the light and compensate for it. How well the various camera models succeeds to achieve a correct white balance indoors is a constant source of excitement among camera reviewers.
Light Color is Measured in Kelvin
Daylight has a bluer (cooler) tone, than, for example, incandescent light that is yellowish (warm). Candles emit warm color that is almost orange.
Light color is measured in Kelvin, and ranging between orange and bluish.
The Kelvin scale originated from the physicist William Kelvin, that in the late 1800s studied how a certain type of coal glowed in different colors depending on how much carbon was heated. The light from a typical light bulb is just over 3000K while the daylight equivalent to about 5500K (but varies widely). Candles are usually closer to 2000K.
The Camera's White Balance Program
Just as the camera has a light measurement for selecting the correct exposure, it also measures the color of the light automatically via the automatic white balance (AWB). This setting, I recommend that your camera is set by default, but the cameras have fixed settings for different types of light as well as manual selection which might be interesting to try out for various reasons. Exactly what choices are available for white balance varies depending on the camera and model, but these kinds of settings tend to be:
Auto White Balance (AWB)
Most cameras typically do well in this setting, if you're shooting indoors in bulbs or fluorescent lighting, you should try one of the fixed settings.
Fixed White Balance Modes, such as shade, daylight, cloudy, incandescent (tungsten), fluorescent and flash.
Measurement of the white balance by shooting a neutral surface (e.g., a white or gray paper) that lets you cover most of the motive. (In practical terms, different cameras differ quite considerably from each other — read the manual.). By this, the camera has learned that the color defects that might occur, for example, that the white paper is slightly yellowish, should be compensated for so that the images will be neutral.
The problem with this setting is that it sometimes becomes too technically perfect — we would like to have a bit yellowish in the picture to create an indoor feel. Some cameras can for this reason adjust the white balance slightly, for example, by making it a bit warmer.
Some cameras let you choose how many Kelvin to set your images.
With RAW Format You Can Control the White Balance at Another Time.
If you shoot in the so-called RAW format, you can later, through a computer, choose the exact color temperature in which the image is interpreted. You would then go around and accidentally have the camera set to bulb while you're shooting in daylight. Back home, you discover that your two hundred images from the day are angry bluish! But by opening the images in your RAW converter (e.g., Photoshop) and change the white balance to daylight, you get a perfect picture and can finally exhale.
Digital camera's image sensor has only one way to see the colors so that the image data (pixels) look identical regardless of whether you set the camera white balance in incandescent or daylight. On the other hand, your white balance setting is stored as a numeric value and then used to interpret the image before it is displayed for you. To change this parameter afterwards, has no negative effect at all on the picture quality compared to shooting the picture with the right attitude from the start — the image raw data is the same regardless of your white balance setting.
Sure, you can change colors even if the image is photographed as JPEG, but you will not have near the same end quality because RAW image contains much more image data (shades of color and contrast ratio). It is easy for the JPEG file "to crack" in the large color adjustments, i.e., the color tones become very pale or changes color. The results tend to show that parts of the image's color seems unnatural for big changes. That is not the case with RAW image after the adjustment.
To shoot in RAW format is therefore the safest you can do if you want a perfect result, but are not sure which white balance setting you need for your subject.
Technically Correct is Not Always the Best
For some images, it is also a matter of creative interpretation of the white balance. It is perhaps more interesting what feels right in terms of image, than what is technically correct.
Finally I would mention that when you change the white balance on your PC (and in many cases via the camera) there are always two sliders.
With the temperature control, you can freely choose the exact color temperature you want. You make the picture bluer or yellower.
The second slider is toner. Dragging the slider allows you to get a white balance with more green or magenta (reddish). If you shoot a lot indoors, such as in fluorescent lighting, you will surely pull this slider to fine-tune the white balance. But for normal lighting situations such fine tuning is not necessary.
Summary and Some Tips
Set the camera on Auto White Balance (AWB), by default.
When you are indoors, try and see if any of the fixed modes (incandescent or fluorescent) provides better color. Just do not forget to change back to the AWB.
Avoid mixing different light sources in your subject — it's very difficult to balance a picture that in some spots is bluish, and at other spots yellowish.
Try using the ExpoDisk - Professional Digital White Balance Filter
With RAW format you avoid all the white balance problems and can freely choose the white balance later on.
