[yt-users] scale on colourbar?

Hi, I'm creating a slice image but it's refusing to tick mark my colour bar properly: http://i.imgur.com/YQBWJ.png pc = PlotCollection(pf, center=position) p = pc.add_slice("NegEscapeVelocity", 2, field_parameters={"disk_vector":disk_vector, "disk_center":disk_center, "disk_radius":profile["DiskRadius"], "disk_potential":profile["PotentialField"]}) p.set_log_field(False) p.set_zlim(0.0, 30.0) p.set_width(8, 'kpc') Is there something simple I've done wrong? I tried rearranging the last 3 lines, but to no avail! Elizabeth