After his confirmation, he was enrolled at the Royal Danish Academy of Fine Arts.
While there, he was awarded several silver medals for his portraits and historical images and earned a reputation as a diligent painter.
[4] Raadsig was occupied with topics from Danish history, especially as it was perceived in contemporary literature.
In 1850 Raadsig made the painting Ingolf tager Island i besiddelse, depicting Ingólfr Arnarson, the first Norse settler of Iceland, newly arrived on the site of what would become Reykjavík, commanding his high seat pillars to be erected.
[5] He was awarded De Neuhausenske Præmier by the Royal Danish Academy of Fine Arts in Copenhagen in connection with his work Vildttyve i forhør hos en birkedommer (1857).