For example:
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Often the posters are driven mainly by the advertising companies which makes them extremely profit driven, which is a very common reoccuring theme in the media, especially film.
One of the most famous film posters is Birth Of A Nation:
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It has everything you need to know, Where/When/About. Obviously the poster itself is fairly dated, however it has the basic foundations of what makes a extremely popular and well done film poster.
Bill Gold's Casablanca film poster is also one of the most iconic posters, and recognised globally:
Saul Bass is also a known Graphic Desinger and Filmmaker. Film posters are a lot more basic and simple, rather than the likes of Bill Gold and Drew Struzan. Often posters nowadays are used as Star Vehicals. Poster makers often take on the idea that by plastering a picture or a name of a huge Hollywood star accross a poster, this will make it more popular. Often this may be the case. At the beginning of modern film studios would own their own actors, rather like how football clubs own their players and buy and sell. This way the advertising team were able to use their actors name as much as possible, making them more sellable.
As advertising and film posters became more prominent in the process of film making graphic designers such as Bob Peak used constructed artist images, Richard Amsel handrawn his posters. Then became the rise of digital, with posters such as Starwars, ET, Batman.
However in recent times theres been a resurfence of artwork, rather like Richard Amsels hand drawn artwork.