Food Photography: White Balance

Sorry for the last days where I updated the blog less frequently but various works and the purchase of a new studio (with all the included bureaucracy) has been keeping me quite busy. " Every cloud has a silver lining" , you could tell me, but unfortunately the day is only of 24 hours (damn!) and it would make no sense to write crap just to post something new.

As I promised in this earlier post I'm starting today a series of posts explaining the various techniques of lighting and shooting that are used in the photography of food.

Let's start on the subject, for so many mysterious, called "white balance".


Light has color


Have you ever noticed how at sunrise or sunset the light has a color different than at noon? Or as in a cloudy day everything seems more "blue-gray" than in a sunny day?
The reason is that light has a color or, rather, a temperature that, conventionally, is indicated in Kelvin degrees.

Despite what you might think at lower temperatures corresponds a "warmer" (ie, tending to red) color of light  while, at higher temperatures, the light color becomes colder (ie, bluish).

You'll wonder "Why should I care about all this almost non-sense stuff?".
If you want to be a photographer you should care about it a lot because our eyes automatically balances the light, mostly eliminating its color,  while both films and digital sensors do not, with the result that, for example, a scene illuminated by a tungsten light bulb will appear in a photo with a pronunced "red" cast.


Here is a simple "table" of colors of light depending on its nature:

As you can see the light of  tungsten light bulbs is red-orange, but also the one from conventional fluorescent bulbs is yellow-orange, despite it seems pretty "white" to our eyes.


Let's talk then about the concept of white balance.


To understand it, just pay enough attention how our brain make us feel "whitish" colored light, such as the one produced by those light bulbs, shifting all the colors so that a light about 2700 degrees Kelvin "hot" would appear similar to sunlight at noon (which is 5500 degrees Kelvin).


With film based photography, there was no way to use a trick similar to the one used by our brain. You had to use filters to neutralize a colored light (ie a blue filter neutralizes, alas it makes white, a red light) or use films specially designed for the different types of light (ie tungsten, the normal old light bulbs).


Digital allows us, instead, to use exactly the same procedure that use our brain, and in an even more efficient way. The white balance can be set before taking the picture, telling the camera which light we are shooting under, or in post production, that is, a photo editing program, selecting a point on the picture where we know that can be found a neutral color (alas a shade of gray).


In digital SLR cameras (but also in many advanced compact cameras) there is a similar menu where you can set the "color" of light of the "scene" you are shooting.

AWB means that the camera will try to "guess" the temperature of the light.
The various symbols depict the most common lighting conditions you can meet (in order the sun at noon, shade, overcast daylight, incadescente bulb, fluorescent bulb, flashlight, exact value, value settable by wheel selection) .

In post-production you can balance the white using various tools, the usually more convenient to use is "levels" where you can see the histogram of the photo and where there are three different eyedroppers: one black, one gray, one white.

The one to set the white balance is the grey eyedropper, circled in red in the picture (which shows the Layers window of GIMP, Photoshop and other programs are similar). Click on the eyedropper to select it then press again with the mouse over an area of the image where there is a neutral color "colored" by the light (eg a white tablecloth or a plate).


You will see therefore change all the colors of the image that will, hopefully, be then similar if you had photographed it with sunlight.



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