is there any special effect in the aforementioned episode of sherlock?
Yes. It was the first time a visual effect was made on a large scale
The Hounds of Baskerville
 Although the series used computer-generated imagery (CGI) in the past, it was the first time a visual effect was made on a large scale.
whatt is "the hounds of baskerville"? Second episode of the second series of the BBC crime drama series "Sherlock" when was it released? 8 January 2012 who is the writer of the episode? Mark Gatiss who is he by profession? Actor, comedian, screenwriter, director, producer and novelist what other shows did he work for? Doctor Who, Sherlock and Dracula what did he do on the last show? Writing and acting what character did he play on it? UNANSWERABLE name a few broadcasters of the show? BBC One and Netflix how did the last broadcaster start its business venture? DVD sales and rental by mail when did it come into streaming services? 2007 who are its rival? Amazon Video how much broadband is consumed by it? UNANSWERABLE did it avoid paying taxes? Yes. In 2018 describe the devices that support its streaming service? Via an internet browser on PCs, while Netflix apps are available on various platforms, including Blu-ray Disc players, tablet computers, mobile phones, smart TVs, digital media players and video game consoles
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The Hounds of Baskerville [SEP] Filming and effects
Throughout the episode, the production crew used split dioptres in certain scenes, a camera technique where two separate camera angles are at the same focus on screen. The episode also includes shots of the hound, which was produced by visual effects. Although the series used computer-generated imagery (CGI) in the past, it was the first time a visual effect was made on a large scale. However, there was no guide for the cast to interact with.