After eight years in the Navy, Preus started his own photography company in 1956. After a while, the company grew to become Norway’s biggest photography business, with a leading photography lab and its own chain store. Leif Preus soon realised the importance of having employees with knowledge about photography, and he was actively working towards building a photo museum. 

The collection became the foundation of the Preus Photo Museum that he opened in 1976, situated in Langgata in Horten. This was the previous location for Preus photo lab, which had to be relocated to a bigger space in Elgstien. One year after the opening, the museum was nominated, along eight other museums in the world, for the European Museum of the Year Award.

In 1995 the collection was bought by the Norwegian state and became the foundation for the Norwegian Museum of Photography – Preus Photo Museum. The collection was then moved from Langgata to Karljohansvern in 1998. On the 26th of May 2001, the new national photo museum could welcome its visitors into the refurbished venue on the fourth floor at Karljohansvern in Horten. In 2005, the museum received its current name, Preus Museum.