Understanding Color and White Balance
Have you ever taken a photo in a room that has fluorescent lighting? Did you photo come out with a green tone to it? Or when it was tungsten lighting you have a yellow tone? Why does this happen? It is the white balance.
What is the white balance? Well, let’s start by explaining color. As you look around you notice trees are typically green, grass is green, certain things are red, others blue, etc. To understand color you must realize that white light contains all colors and black none. As white light falls on a surface certain wavelengths are absorbed and certain wavelengths are reflected. Let’s use grass or plants as an example. Where do they get their green color? Well, in truth they are not green, but simply reflect green light. In fact if you place a plant under just green light it will not do well. Why? Because it can’t absorb green light but rather reflects it.
So the color of an object is determined by the wavelengths it reflects back. Remember the photo is a snapshot of the wavelengths of light be reflected from objects and captured by the sensor. I don’t know if you ever did the experiment where you take three lights, one blue, one red and one yellow and shine them on a single spot. The resulting color from mixing the three prime colors is white!
So the perfect white reflects all wavelengths back. When we are photographing there are various shades of white and depending on the main source of light that white will change. Your eye makes the white balance correction automatically. Cameras can do an automatic white balance correction which in many situations works but not always. The camera needs to be told or to work out what is really white. It needs to know that because it is in a strong tungsten environment that white needs an appropriate correction or it will come out yellowish.
If you buy a white balance filter or card you take a photo of it or using it and then tell the camera this is white. It then corrects how it sees things to make this white. How?
When we talk about white balance we talk about temperature. No, we are not saying the warmer it is that there is an impact on temperature. No! Imagine a scale for 0 to 50000 Kelvin. If we have an ideal photo and start with a WBO set at 0 the image has a strong blue toning or appears colder. As we slow move up the scale the image slowly loses the blue tone and becomes warmer. Tungsten lighting has a white balance around 2850k. If the photo was taken using tungsten lighting it will look more life like. If it was taken outside it will appear strongly blue. Fluorescent lighting is around 3800K and flash around 5500k. If you are outside it is around 5500k as well. However if it is cloudy it is around 6500k.
So as you can see depending on the lighting the WB in terms of kelvin changes. Now, what if you have several sources of light such as flash and outside or natural light? Or in an environment with Tungsten and flash? You can trust the camera’s automatic WB or like most professionals determine the right WB. An alternative is to take the photo in a RAW format with your camera and correct the WB using Photoshop. While, I may adjust the WB in Photoshop to achieve a certain result I have found setting the WB correctly upfront can save a lot of time and headache. To be honest even though Photoshop RAW as a WB dropper which allows you to select something off white to determine the WB it is not always right and you can end up with inconsistency with your photos. When we are photographing weddings, we determine the WB inside the church or facility first. We do record in raw so we can still adjust but this makes life as I said much easier. If you are doing videography determining WB is more important. There are plugins in Premier Pro to help correct WB, but to be honest it is much harder. Having the WB correct upfront will prevent a lot of headache and hours of editing.
You can buy a WB board, reflector or filter for your camera. Or you can photography something white. In the DSLR menu you can set it to a manual WB. It will then ask you to select the correct image. I always recommend a few things:
1) Make sure you have the camera set to the same settings you plan to use it with when you take the WB image
2) When you do set the WB take a photo and look at it to see if it looks correct. Your eye knows if it looks yellow or blue. It should look lifelike. If it is wrong do it again.
3) Where possible take your images in a RAW format (you will need the right software such as Photoshop to process RAW files
4) Remember as you move around and the lighting changes so will the WB
5) With professional video camera you may be asked to do a BB or black balance
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