Image Quality Comparison
Click each picture for a full-size image.
The difference between quality settings is quite apparent. Shadows are considerably more realistic when using the extreme settings over very high -- they're not only smoother but also softer in certain places where objects are not casting such a harsh shadow. Extreme settings also offer more realistic lighting effects and objects such as rubbish bags have more definition.
We see the same variations between the very high and high quality presets as well. The high quality settings make use of even more crude looking shadows that feature less detail. You'll also spot another big change in the polygon count as you can see objects such as the arched windows are much more jagged now.
The differences between each quality setting are more subtle but they are still present in this next series of screenshots. Once again, the extreme setting offers more detail and softer shadows over the very high and high presets. The tree's shadow looks much more realistic, the tree trunk has more definition, and the shrubs around the tree are only seen with extreme quality.
When comparing the very high and high presets the biggest difference is the loss of detail. Most of the grass under the tree is gone while the mud in front of the tree and on the road is virtually gone.