White balance is an interesting topic. How the colors of an image are represented are sometimes a subjective thing and sometimes not. Getting good skin colors on a portrait can make or break an image.
White balance is matching the color of your image to a known color temperature. For instance a standard incandescent light bulb has a color temperature somewhere around 2800 degrees kelvin while the sun has a color temperature between 5500 and 6000 degrees kelvin (k). These temperatures are not random numbers made up to confuse photographers. The Sun’s surface temperature is about 5773k so there is a correlation between its actual temperature and what we call daylight white balance in photography.
The lower the temperature given off by the source of the light the more orange it is. The higher the color temperature is the more blue the light is. If the light color is too low, as in infrared, the light will not be picked up by the photographic medium, as in film or a photo sensor. On the other end of the spectrum is light nearing ultra violet which is quite blue and again beyond the range of photography.
While the Sun is a main sequence star with, thankfully, a 10 billion year life cycle, most stars you can see in the sky are larger, faster burning, giant stars with surface temperatures up to 10,000k.
Our eyes and our brain do a pretty good job of correcting the white balance we see normally. Cameras can be way too literal it the way they process colors. Unless we get specific about the lighting conditions, colors in an image can be way different than what we see with our eyes.
Assuming that you have set your camera for the proper prevailing color temperature, daylight, cloudy, tungsten, etc. the colors should be pretty close to what your eyes see. If you are using an auto white balance mode on you camera the camera will take a best guess of what the colors should be.
In post processing we can adjust the color balance to what it should be or we can apply a color correction to give an image the impact that we perceived when we took the image. We use the white balance dropper in your choice of image processing software to choose an area meant to be white.
Beyond using an algorithmic method like the white balance tool, we can also adjust the white balance to suit our eyes. We can warm or cool the colors of an image by adjusting the white balance slider (and the tint slider see previous article) If an image is too warm with white things looking orange we can apply a blue cast to the image to bring it back to what we want the color to be. Alternately we can also apply an orange cast if the image is too cool.
So if we had lit the moon with an incandescent light when the color balance was set to daylight we would end up with a very orange moon like on the left side of the moons above.. To correct the color balance to get the moon back to the expected white moon we would move the color balance slider towards the 2800k side to correct the moon back to the middle ground.
And the opposite is also true, warming a color balance by introducing a lower temperature will turn the blue moon white then orange.
