Generally, I find that many effects with Topaz filters introduce haloing
around areas which have contrasting tones with other areas: Like a light
sky and darker mountains. I love a lot of the effects and I found that by
putting the sky on one layer and the mountains on another and processing
them separately, I don't get the haloing effects. You can do it with masks,
also, but the simplest way is to "select, separate and then process."