The need to understand white balance comes from the ugly looking yellow, red or green tones that appear on the shots you take, completely giving the picture a different feel to how you saw the scene with your naked eyes. This happens because different types of light have a different ‘temperature’ and that casts different color tone. Ever clicked a photo under street lights and wondered why the picture appeared orange? Now you know.
Before we delve more into color temperature we need to know the measurement unit. Kelvin is the unit for measuring color temperature. It is very similar to Fahrenheit and Centigrade. So why is temperature associated with color? Let’s take an example. Imagine a black colored metal being heated over fire. When it starts getting hot the first color that you see is red. As the temperature increases the metal starts emitting yellow light, then white and in the final stages blue. When we speak of temperature of a color what we really suggest is the color that radiates from a black body when it is heated to a certain temperature. The temperature of the red color is relatively ‘cooler’ when compared to when the metal is white hot. Again, at its hottest the color that emanates is blue. This is why in photographic parlance red is considered ‘cooler’ compared to ‘yellow’ or white or blue (which is a warmer tone).
Different types of light casts a different color tone on the pictures and this necessitates a step of color correction. Usually this is done using the in-built color correction tool that is available in all digital cameras. All digital cameras come with an Auto White Balance (AWB) option in them. Selecting it allows the camera to take the best guess about the available light and use the right color correction to negate the color cast. Having said that, however, rarely do professional photographers feel happy by simply setting the white balance at auto, because the camera never has the same versatility as the human eye and that invariably means the way we see things in any lighting condition may not match with what the camera sees.
The solution is to manually set the color temperature to ensure that you get it right. Thankfully most digital cameras also come with a set of pre-determined white balance options which are marked as Tungsten, Fluorescent, Daylight, Cloudy and Flash, apart from the above Auto. Selecting any one of these will give you the right color temperature for that particular condition. For DSLRs, however, you have an extra option where you can manually enter the color temperature so that the camera knows what color cast to adjust for.
We have been speaking of color temperature and color casts, so which color emits what temperature? A candlelight emits what is known as a reddish tone and is usually measured between 1000-2000 K. To compensate for the same you will need to either manually set a 1000-2000 K as the color temperature or use the candlelight option to get the right white balance. Similarly a tungsten lamp will have a temperature of about 2500 K and a daylight condition will have a temperature of 5500 K and so on.
Finally, you could set the white balance in your camera by giving it a point of reference on what true white is in the available lighting condition. To achieve this, different cameras offer different methods but generally you will need to point your camera towards a white surface (I do it using several sheets of white paper held perpendicularly and against the light) and take a test shot. Once the test shot is taken the camera adjusts the white balance to ensure that the colors appear correct.
Next photography lessons:
Photography basics 1: Tips to Choose Your First DSLR Camera
Photography basics 2: Understanding Camera Exposure
Photography basics 3: Understanding Camera ISO
Photography basics 4: How Does Your Camera Image Stabilizer Work?
Photography basics 6: How Your Digital Camera Sensor Works