Are you asking how to use it or are you asking what it does?
I shoot RAW, so I don't use it (adjustments are not applied when you shoot RAW... you apply all adjustments when you process the images on the computer.)
As for what it does... white balance "shift" and white balance "bracketing" are two different features, but usually lumped into the same menu.
On my 5D II, for example, the rear dial controls the white balance "bracketing" but the 8-way navigator (joystick) controls the "shift". The shift simply pushes the white balance away from whatever it would normally use... e.g. if you want the image to be more "blue" you could use the navigator to nudge the dot toward the blue direction. There's a red/blue axis and a green/magenta axis. The "bracketing" is handled by the dial... if you roll it right then it'll spread out some points along the red/blue axis... causing the camera to save 3 images from each exposure you take. One will be balanced according to camera settings (which could include the "shift") and the other two will be bracketed... one more red, the other more blue. If you roll the rear dial left (counter-clockwise) it'll return to the middle point (no bracketing) but if you keep rolling the wheel the points will spread out in the other axis... along the green/magenta axis.
WHY you would do this could have various reasons... you might be unsure of the white balance and want to collect a spread. You migh thave wonky lighting where no single white balance works for all the various light sources and want to allow the camera to record multiple options.
If you only have a single light source (or if all light sources are the same type) then you can either dial in the white balance based on the type of light or use the custom white balance option with a gray card.
I shoot RAW -- so white balance isn't applied to the image. But I can still shoot a gray card and use that as the reference when applying white balance in post processing, then apply that change to all other images shot in the same lighting (I use Aperture, but Lightroom and Photoshop can do this as well and it's pretty simple.)
Does that help?
Tim Campbell
5D III, 5D IV, 60Da
