Complex sentence: Largely ignored by filmmakers due to the difficulties in filming them, the producers decided to concentrate on invertebrates due to advances in lens and camera technology that gave the makers an opportunity to film invertebrates at their level.
Split into simpler sentences: Largely ignored by filmmakers in the past, due to the difficulties in filming them, the producers decided to concentrate on invertebrates. Advances in lens and camera technology gave the makers an opportunity to film the creatures at their level.