Is there such thing as perfect white balance? Some people worry over getting white balance technically correct. And there are products on the market such as Expodisc that try to do exactly this. In my opinion however, you don’t need to obsess over white balance. Why? Because our perception of color is a guess to begin with.
The following picture appears to be a “white” business card lying on a black background.
I have many other “white” business cards. By themselves, each card looks white. But when placed side by side, it’s apparent that they are all really different shades of (off-)white.
Two things to note here:
1- Many white objects aren’t truly perfectly white.
2- Despite that, these objects appear white to our visual system when viewed in isolation.
Our visual system has to guess the color of objects since the input is ambiguous. A white card under slightly green light will reflect slightly green light. So will a slightly green card under white lighting. Multiple scenarios can lead to the same visual input. Our visual system will nevertheless make an educated guess as to the object’s real color (these guesses tend to be very good) and that’s what we perceive.
When it comes to setting white balance, I wouldn’t worry over getting white balance 100% correct. In a mixed lighting situation with two or more different light sources of different colors, there is no ‘correct’ white balance for the scene as each light source has its own correct white balance. Perfect white balance is not always possible and it isn’t even necessary. What I would strive for is to make the appearance of the final image fit your intent. If it looks right then it looks right- it doesn’t need to be any more complicated than that!
Do white objects even need to appear white?
There are some cases when the correct white balance does not make white objects appear white. There are certain lighting situations where our visual system’s “white balance” won’t completely adjust for the lighting. A good example is 'golden hour', the hour before sunset where everything takes on a golden tingo. In this case you don’t necessarily want to make white objects appear perfectly white if you want to maintain that golden tinge of the original scene.
Try our freeware white balance + highlight recovery filter. It white balances the image and recovers highlight detail that is normally thrown away in the white balance process.
For further reading, check out Understanding White Balance at cambridgeincolour.com.