From Indiewire:
Michael Parbot, a French journalist who gained unprecedented
access to the 'Empire' production, contributed his footage to two
documentaries: “SPFX: The Empire Strikes Back,” a
behind-the-scenes look at the film's special effects, and a 1980 Dutch
TV program showcasing lightsaber rehearsal footage and interviews with
the cast.The first made it onto the trilogy's Blu-ray release in 2011, but the Dutch program has only been seen in near-unwatchable snippets, appearing last in 2012 with 15 minutes available. Finally though, our clearest and most extended (30-minute) look has arrived, and it features fascinating conversations with Irvin Kershner, Mark Hamill, and a bashful Harrison Ford.
George Lucas himself is notably absent, but the doc shows instead the incredible technical work done by both the actors and crew, facing such situations as shooting in Norway's extreme weather to depict Hoth, and also how to wrangle Tauntauns and Wampas as well.