White Balance

17/11/09

Most light sources are not 100% pure white but have a certain "color temperature", expressed in Kelvin. For instance, the midday sunlight will be much closer to white than the more yellow early morning or late afternoon sunlight.

Normally our eyes compensate for lighting conditions with different color temperatures. A digital camera needs to find a reference point which represents white. It will then calculate all the other colors based on this white point. For instance, if a halogen light illuminates a white wall, the wall will have a yellow cast, while in fact it should be white. So if the camera knows the wall is supposed to be white, it will then compensate all the other colors in the scene accordingly.

Most digital cameras feature automatic white balance whereby the camera looks at the overall color of the image and calculates the best-fit white balance. However these systems are often fooled especially if the scene is dominated by one color, say green, or if there is no natural white present in the scene as show in this example.
















The auto white balance was unable to find a white reference, resulting in dull and artificial colours.


















The auto white balance got it right this time in a very similar scene because it could use the clouds as its white reference.

Most digital cameras also allow you to choose a white balance manually, typically sunlight, cloudy, fluorescent, incandescent etc. Prosumer and SLR digital cameras allow you to define your own white balance reference. Before making the actual shot, you can focus at an area in the scene which should be white or neutral gray, or at a white or gray target card. The camera will then use this reference when making the actual shot.

My own personal preference ( otherwise known as lazy option ) is to leave the camera on Auto White Balance mode, and subsequently make any adjustments that are necessary in my post processing package, in my case Lightroom. This particular software has a drop down menu bar listing eight or so different White Balance settings, and these can be applied to the image by one click.

PRACTICAL TIPS by Simon Lutter

This only relates to colour photography.

White balance is one of those confusing things that are there to make photography even more challenging! It is worth finding out a little more though because when you have got to grips with it it is well worth it because it can make your images so much more than a snapshot and more of an image to be proud of.

What on earth is white balance? Well all cameras have a default setting to see 18 1/2 % grey and that is how they judge their colour balance. They dont see true white. Have you ever taken a colour photograph of snow or a beach scene and found it has come out rather blue? This is because the camera is not able to register the correct white balance.

To keep things simple in this really complex aspect you need to recognise the type of light you are shooting in. Your camera will have icons to illustrate the type of lighting you are photographing so do make use of them. You dont need an expensive colour temperature metre to read the light temp.

All lighting has a colour measurement, or temperature and it is enough to know for now that all you have to do is look at the light source and adjust your camera setting accordingly! Of course you can always rely on the camera to select the correct balance(AWB) but where is the fun and creativity in that?

You will find that you have tungsten, flash, shade, cloud, neon(strip light) bright sun and perhaps a few other settings too to choose from. Check out the settings and see. Why not try this? Take a photo under strip light in Auto mode,- or any other custom balance, then reset your camera to the strip light icon and see the difference! I bet Auto comes out rather green! Or try taking a photo in Tungsten( household bulb- comes out yellow) and see the difference when you reset the camera to Tungsten).

How do you overcome the blue in snow and beach scenes? Simple- overexpose the camera one to two stops.

However you can also use the white balance to gain different effects-warm up or cool down your images in a creative way so why not give that a go too?