White balance is the calibration of the white point of an illumination, where it is matched to a set standard. Most digital cameras have an automatic white balance system that tries to correct the recorded colors so that the whites (and all other colors) appear normal to the human eye.(Ang, Tom, Fundamentals of Photography; the essential handbook for both digital and film camera's, pp343).
Until recently when I experimented with it, i really did not quite understand what white balance was for , but now i do. In this exercise, i took images of the same objects in direct sunlight, shade and auto and compared them.
 |
| Image 1:AUTO WB, ISO 3200,85MM,0EV,F4.5,1/500 |
 |
| IMAGE 2:WB DIRECT SUNLIGHT,ISO 3200,85MM.0EV,F4.5,1/5 |
 |
| IMAGE 3:WB SHADE,ISO 3200, 85MM,0EV,F4.5, 1/500 |
As can be seen from the above images shot in Auto , direct sunlight and shade white balances, the image contrats are different. Shooting under this late morning condition and with such high ISO, the camera has adjusted automatically in image 1 for the ligh condition. In image 2 shot in direct sunlight white balance , it may have appeared better if taken truly under direct sunlight rather than from a balcony which i did. The high colour temperature in image 3 with shade white balance tends to make the background colours come very close to the colour of the yellow containers. I took another set of 3 pictures under the same conditions bou with a lower ISO to see the effect.
 |
| Image 4: Auto white balance, ISO 1250,70MM,0EV,F4.5, 1/250 |
 |
| Image 5: Direct sunlight WB, ISO 1250, 70MM,0EV,F4.5,1/250 |
 |
| IMAGE 6:WB shade,ISO 1250,75MM,0EV,F4.5,1/200 |
By reducing the ISO to 1250, I was able to remove some grain from the images rendering them a bit sharper. You need to look closely to tell the difference. Pixel pipping is something I have become accustomed to. With powerful camera's these days you can set your ISO to 12,800 and still get almost noise free images. Unless there is need to make very large prints , the difference is hardly noticeable. So ISO 12800 on a Nikon D4 can appear as ISO 3200 on a Nikon 3100 camera. Such is the level that its possible to take pictures in near darkness with todays expensive modern cameras.
When we take pictures, adjusting properties like ISO, White balance, aperture and shutter speeds have direct effects on the final image. We must know what to correct for at the beginning and depending on the light situation.
On my Nikon D7000, the white balance settings listed are:auto, incandescent, fluorescent, direct sunlight, flash, cloudy, shade and various other colour temperatures to choose from. I was at a wedding a while ago and the interior of the venue was reflecting different colors. When I took pictures I realised that the images were affected by the intensity and color of light in the venue. I did not know about white balance at the time and even though my camera was set to auto, the effect of the colours were so strong that the camera could not correct adequatly for it. With the benefit of hindsight, i now realise that i could have changed the white balance to suit the particular light conditions.
