Understanding Exposure In Digital Camera Part 3
White Balance in Digital Photography
Last week I talked about controlling exposure by using ISO, Shutter speed, and Aperture. These variables control the exposure, which is brightness and contrast of the image. Exposure does not play a big rule in colour rendition, so this week I am going to explain how to create better colour in your photos.
You can control the colour of your photos by using White Balance.
Many photographers avoid using the White Balance (WB) setting in their camera simply because they think the camera can take care of it or, if necessary, they can make the colour adjustment later in post processing. This can be true but there are certain variables which can cause an undesirable color cast in our images and sometimes post processing will not help us a lot (especially if you shoot in jpeg format).
In this article I am going to explain a basic definition of White Balance and give you some tips on when you should consider using a custom White Balance.
What is White Balance?
You’ve probably noticed when checking and reviewing your digital photos that at times images can have an orange, blue, yellow etc cast to them, although to our eyes the scene looked quite normal. The reason for this is that different sources of light have a different ‘color’ (or temperature). These differences in color/ temperature range from the very cool light of a blue sky through to the very warm light of a candle.
We don’t generally notice this difference because our eyes adjust automatically for it. 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 brain to make these adjustments automatically and will faithfully, accurately record for the predominant (and usually invisible to us) color temperature.
What is Auto White Balance?
Each digital camera has the data of thousands of images built into its processor. When you use any of the auto modes (Auto White Balance, Auto Exposure, Auto area auto focus, etc.) the camera compares the scene to the data of these images and selects the one that is closest. The result might be close or be quite far from accurate color and exposure.
You may have noticed that the newer digital camera take better photos. It is not because these cameras are better made, but mainly because the manufacturers add more data to the newer camera to use as references.
When should I use Auto White Balance?
That being said, if you have a newer digital camera, and are taking pictures with only one source of light, the Auto White Balance will create a decent image for you. If there are more than one source of light (e.g. daylight from a window and tungsten light of an indoor lamp) the chances are higher that your camera can’t make the right decision, which will result in a heavy color cast in your image.
How do digital cameras measure the White Balance?
Generally speaking, digital camera searches for 18% grey in the scene, and whatever resembles closest to 18% grey will be used as a reference to grey and the colors adjusted accordingly. This is why photos in a forest with no white or grey present in the scene will often end up with a deep green cast over your images.
Should I use auto or custom White Balance for every single photo?
Here are three golden rules for when to use Auto White Balance:
1- You have a newer digital camera
2- You have something white or grey in your subject
3- You have one dominant source of light, not a mixture of light sources.
If none of these apply, then a custom white balance setting would be a good option, especially if you shoot primarily in jpeg format.
What is a custom White Balance?
In custom White Balance you tell your camera what is white or grey and the camera will set the other colors for you. Your camera will remember this custom setting until you change it again.
Does this mean that I have to do custom White balance for each and every picture?
As long as the light source and its brightness stay the same you don’t need to change the setting. When you change location (for instance from shade to sun, or from one room to other room) you will need to redo the Custom White Balance.
Look at these photos and see how different White Balance settings can change the colours.
To learn more about Digital Camera Photography visit our Upcoming Classes page to find a workshop that covers your questions.
Stay tuned for our next Photo tip.
Ted and the Omnilargess Team