So white balance is something you hear about and to be honest most of us ignore in the beginning. Most cameras have an "auto-WB" mode and for the most part that's pretty accurate and works. However, in extreme conditions e.g. indoors or night-shots the camera can get confused... badly.
So white balance? What is it?
Well my understanding is that different light sources (the Sun, street lights, indoor blubs) have different "temperatures". In other words, they emit a slightly different colour. Depending what colour the light source is you should set your camera to that. Alternatively, you can, and should, shoot in RAW and fix it later (but we'll cover that in another post). The point being that white bits should then still look white and not oranage for example.
However, that can be quite tiresome and so people often just leave it on Auto. But even with a decent DSLR your camera may still have a hard time decerning the white balance in auto-mode.
I took this shot last night near Glencourse Reservoir. As you can see there is a dreadful orange colour cast in the clouds - something I would have never have noticed a year ago. This light is coming from the street lights of Edinburgh - this is "light pollution" - something you can clearly see in the sky when you are driving into most cities/towns at night if there are some clouds in the sky.
Here you can see that I've corrected the white balance in Adobe Camera Raw and immediately there is an obvious different. You can see that the clouds are now the correct colour and also the sky has become a dark blue colour. Although the actual sight may have looked like the first image, your brain (or at least mine) seems to sieve out all the abnormal colours and what you're looking at just seems normal. It's not till you correct the white balance that you see the difference.
I should point out though that although you can do this after the event using a RAW file (instead of JPEG) by fixing it in post production, that's not a efficient use of your work flow and you should set your camera's white balance for each shoot. This saves a lot of time afterwards. Just don't forget to change it back afterwards! So hope that explains something that took me months to figure out.
Comments and critisicms welcome.