XaoS performs many optimizations, but fairly often this is not enough. In order to keep a high framerate, XaoS automatically lowers the resolution of the image, increasing it when there is time for more calculation. This feature is enabled by default when animating, but you might also like to enable it for new images (which makes the image `come into focus' when it is recalculated from scratch for whatever reason), or disable it completely if you don't like it.
In the scripting languge, the keyword should be one of the following:
Disable dynamic resolution
Use only for animations (default)
Use also for new images