If you are trying to achieve an in-camera Orton effect, then this new article is a must-read from film photographer Alexis Cuarezma. Hoya recently partnered with Cuarezma to test the Hoya White Mist and Hoya Black Mist diffusion filters.
Cuarezma notes the similarities and differences in halation between the two filters, gauges the diffusion strength of each filter, and shows final examples of what these creative filters can do.
Check out the writeup and accompanying video as well as Cuarezma's new educational photography website Strike the Lights.