With Bayer sensor based cameras setting the white balance for a photo is a relatively easy task. You’d normally have two sliders you can adjust to reach the desired balance. Instead of those sliders Sigma Photo Pro has a color wheel to adjust the white balance. A relatively simple and easy to use tool. But there is one catch, you have to start with the right white balance preset.
The presets do a lot more than just set a starting point within the color wheel. Each white balance preset has a difference response to certain parts of the light spectrum. Choosing the right preset to begin with results in a much better balanced photo. Sometimes the differences are very subtle, like between overcast and sunlight. But for instance incandescent is very different from all others.
In the collage below you can see the effect on a normal daylight photo. On all four versions the white balance was set using the color picker on the same spot. The top left one has overcast set as preset, top right is set to incandescent. Bottom left has shade as the preset and the bottom right is fluorescent. As you can see it is evident that the preset has a big influence on the end result.
Here is another example, shot under artificial lighting. The version on the left has incandescent set as the white balance preset. After using the color picker to choose a neutral grey the photo has a very good and realistic white balance. The one on the right has sunlight set as the preset. Using the same spot with the color picker results in a photo that is quite far off. Black turned blue and yellow became over saturated and shifted to green.