White Balance and Color temperature

White Balance

White Balance is an aspect of photography that many digital camera owners don’t understand or use – but it’s something well worth learning about as it can have a real impact upon the shots you take.

White balance (WB) is the process of removing unrealistic color casts, so that objects which appear white in person are rendered white in your photo. Proper camera white balance has to take into account the "color temperature" of a light source, which refers to the relative warmth or coolness of white light.

When examining shots after taking them that at times images can come out with an orange, blue, yellow etc. look to them – despite the fact that to the naked eye the scene looked quite normal. The reason for this is that images different sources of light have a different ‘color’ (or temperature) to them. Fluorescent lighting adds a bluish cast to photos whereas tungsten (incandescent/bulbs) lights add a yellowish tinge to photos.

We don’t generally notice this difference in temperature because our eyes adjust automatically for it. So unless the temperature of the light is very extreme a white sheet of paper will generally look white to us. However a digital camera doesn’t have the smarts to make these adjustments automatically and sometimes will need us to tell it how to treat different light.

So for cooler (blue or green) light you’ll tell the camera to warm things up and in warm light you’ll tell it to cool down.

Adjusting White Balance

Different digital cameras have different ways of adjusting white balance so ultimately you’ll need to get out your cameras manual out to work out the specifics of  how to make changes. Having said this – many digital cameras have automatic and semi-automatic modes to help you make the adjustments.
Modern digital cameras feature several white balance presets, as well as custom settings allowing photographer complete control over the white balance. Here we will cover them briefly and mention effects they have on photos.

  Daylight (approx. 5500 K): This white balance setting adjusts the digital camera to make colors appear natural when shooting in sunlit situations between about 10:00 AM and 4:00 PM (mid-day). Good thing to remember is when sun is lower in the sky with more red light, the scenes photographed using this setting will appear warmer than normally seen with our eyes. Also note that indoor scenes lit with incandescent lights (e.g. tungsten) will look very warm.

  Cloudy (approx. 6000 K): Even the symbol is cloud, think of this white balance setting as Cloudy/Twilight/Sunset setting. It warms up cloudy scenes as if you had  a warming filter, making sunlight appear warm, but not as much as the shade setting. You might also consider using cloudy setting for shooting people, as it will produce warm skin tones, with much more subtle effect than shade setting.

  Shade (approx. 8000 K): Used for shadowed objects under blue skies, removing the blue color cast. This setting is also used to warm up the scene, and can be used for same purposes as cloudy setting, but with much more pronounced effect. We suggest that you try out both settings, and see which you prefer.

  Tungsten Light (approx. 2700 K): The tungsten setting is designed to give natural results with quartz lights. It also reduces the strong orange color that is typical when photographing lamp-lit indoor scenes with daylight balanced settings. Since this control adds a cold tone to other conditions, it can be also used creatively for this purpose (e.g. make a snow scene bluer).

  Fluorescent Light (approx. 4200K, 5000K, 6500K): White balance setting to be used for fluorescent lights. Since the fluorescent lights usually appear green in photos, this setting adds magenta to neutralize that effect. Usually it comes in 3 settings for finer tuning. You can use this setting creatively, if you wish to add pinkish tones to your photos.

 Flash (approx. 5400 K): Lights from flash tend to be little “colder” than the daylight, so this white balance setting warms the scene a little bit up. It is very similar to cloudy setting, and can be used in similar conditions.

Manual White Balance Adjustments

In most cases you can get a pretty accurate result using the above preset white balance modes – but some digital cameras (most DSLRs and higher end point and shoots) allow for manual white balance adjustments also.

The way this is used varies a little between models but in essence what you do is to tell your camera what white looks like in a shot so that it has something as a reference point for deciding how other colors should look. You can do this by buying yourself a white (or grey) card which is specifically designed for this task – or you can find some other appropriately colored object around you to do the job.

white is white (not grey, bluish or yellow) etc. Now, the question is why and how would the latter even be possible? You see, our eyes are amazing photo-sensitive devices, and they adapt to not only the amount of light available (seeing in dark), but also to the ambient temperature of the light. The camera’s sensor though, is not so adaptable, and sometimes it needs our help on understanding how to process the photo. This effect is most pronounced in so-called mixed lighting conditions.

What is Color Temperature ?
The white balance scale is based on the thermodynamic scale of Kelvin ratings as illustrated on the figure below. According to this scale, every light source is assigned a color temperature. Lower color temperature values appear “warmer” (redder), while higher values produce “cooler” (bluer) cast to the photo.

So considering example photo above, if we set white balance to daylight setting (approx. 5500 K), and catch a tungsten light source – a lamp (approx. 2700 K), it will appear yellow-orange to our digital camera (as seen in first photo). Consequently, if we set white balance to Tungsten setting, and catch an object illuminated by daylight light source, the object will appear blue (see wall in mouse over photo).

In most cases, if the white balance is set to auto, the camera will take care of guessing which is the most appropriate setting, and most modern cameras do a decent job of it, however, taking manual control over white balance, opens a whole new range of creative possibilities.