<<<-- Originally posted by Balazs Rozsa : when I go into a shop which has 100 Hz and normal TVs put next to each other, the 100Hz pictures look much softer. This is why I think converting to other formats from an interlaced format will not give too good results. And I think this is why they rarely put 100 Hz and normal TVs next to each other. -->>>
What you are saying may be true but the example is not the best. 100 Hz TV have cheap electronic in order to do the conversion. It is not a good conversion. In theory if you apply the right math any format could be converted in another format without visible degradation if the new format has enough BW and resolution . Still too often though we see scaling done with decimation and interlaced to progressive done taking away every other half field. Both tricks are followed by integration with some amount of low pass filtering. results are pretty bad.