I will start this article by saying our eyes and brain deserve some accolades, they have successfully white balanced every scene for us, for this reason as normal individuals the whole concept of white balancing is of no real use to our daily lives. What this means is a white paper is a white paper under any lighting condition to our eyes.
But in the real sense every light sources have their own specific colour tint ranging from warm to cold, from our knowledge of colour theory and daily experiences orange indicates warm and blue indicates cold. For instance, Candle light has a very warm colour tint and is therefore deep orange while tungsten (Household light bulb) has a lighter shade of orange. The Colour tint/temperature is measured using degree kelvin. It ranges from 1000k-10000k
The Kelvin Temperature Scale gives a numerical range of values to the colours tints we are most likely to come across. Just as I said earlier this values means nothing to our eyes but to the DSLR makes a whole lot of difference.
White Balancing in a DSLR is therefore measuring the light sources colour tint accurately based on knowledge of the light conditions and using this information to get the correct colour of white and ultimately balance all other colours.
What this definition simply means is to white balance an image is to pre-set the colour tint on your DSLR so as for the Camera to properly balance the colours and see white as white.
For instance, in a room lit with a Tungsten Bulb (Household light bulb) the colour temperature according to the Kelvin Scale is between 2500-3500 so you either set your Camera white balance to to Tungsten light which is approximately 3200k on my DSLR. What this does it that it informs your Camera that the light source is warm and so the white may have a shade of orange and it return the DSLR compensates for that giving a final result of balance in the colour on your subject.
White Balancing my Images
Most DLSR manufacturers use the knowledge of colour tints from lighting sources to include white balance presets This is an attempt to make white balancing easier for photographers. The default Presets on my DSLR include
-Auto White Balance
-Daylight Approx. 5200k
-Shade Approx. 7000k
-Cloudy Approx. 6000k
-Tungsten Approx. 3200k
-White fluorescent light Approx. 4000
-Flash Approx. 6000k
I took a few shots of a white cup to further explain this simple concept. The room was tungsten-lit and I added a flash to cool down the colour. (4000k-5000k). Now let’s take observations of the various images.
Auto White Balance: The DSLR was able to get the right White Balance in this image as a result of the colour(white) of the cup. It made it more accurate. 4600k. The principle behind is it looks out for a reference point in the scene that represents white. It will then calculate all the other colours based on this white point and the known colour spectrum.
Daylight: 5200k, The Colour of the image here is almost correct. But we can sense a bit of warmth (.This can be corrected during post-processing (Photoshop, Lightroom).
Shade: 6850k. This is intended for a very cool lighting scene, and as a result looks warm when the scene Is not as cool as approx.. 7000k.
Cloudy: 5950k. Looks less warm compared to Shade, which shows that the correct white balance for this image is towards a lower kelvin degree value.
Tungsten: This has the lowest Kelvin degree i.e 3250k and we can see that the image appears blue. This is because of the flash colour tint added (i.e I shot using an external flash). If you ever want to use tungsten preset the light source has to be only tungsten bulbs (The filament used in making the bulbs has a colour tint of 3000k)
White fluorescent light: 4000k. Just as in the case of Tungsten the image appears blue because the light source is cooler (flash colour tint).
Flash: 6200k. The Flash colour is obviously wrong as the image appears warmer and white cup looks orange.
In summary the Auto white balance was closest to the correct white balance and Cool(High k) presets like Shade and Cloudy appear orange because the scene is less cool so the warmth added to compensate becomes excess and therefore leaves the image looking orange. Also for Warm presets like Tungsten and White Floursecent light the images appear blue because the scene is less warm so the cool added to compensate becomes excess and therefore leaves the images looking blue.
We have said a lot on getting the right white balance.
-Know your lighting scene and
-set your Camera using either its presets or
-use the Custom setting and define the best.
This of course is simply knowing the rules of photography, and after know them feel free to be creative and break the rules. You can decide to set your DSLR to either Tungsten or White Fluorescent Light preset in a cooler scene (say 5000k) and end up getting a blue looking image. This is useful when you want to get your image a calming, reflective or sober feel.
You can also decide to set your DSLR to a Cloudy or Shade in maybe a daylight condition(5000k) and get a warm looking image in return. This can be used to show happiness, warm, excitements etc.
There are many more instances of how to properly white balance a scene using grey cards, corrective gels, coloured gels, Photoshop or Lightroom etc. These are beyond the scope of introduction to white balancing and I might go into details on any of them at a later time. But for now pick up your DSLR explore different scenes(lighting conditions) and see what effect using the each Camera presets have on your final images. Get Creative and as I always say keep practicing till you can’t get it wrong.