The Birds (movie)
The movie had many technical difficulties. It was challenging to make. There were many special effects for the birds. The sodium vapor process ("yellow screen") was used for the attack scenes of the birds. The process shoots two images at the same time and overlaps them. SVP was better for the fast-moving wings of the birds. Blue backing and sodium matter and optical printers were also used. The movie was nominated for an Academy Award for best special effects.