In 1849, Moulin opened a photographer's studio at 31 bis rue du Faubourg Montmartre and started producing daguerreotypes of young girls aged 14 to 16.
He taught photography, sold photographic equipment, and had a backdoor installed to his studio to dodge further legal problems.
In 1856, Moulin made a photographic trip to Algeria, with a tonne of equipment, backed and financed by the French government, which allowed it to gain benefit from the structures of colonialism.
There, he met technical difficulties due to variations in humidity, work in the open, and the quality of water, but managed nonetheless to extensively document the benefit of French colonies in Northern Africa.
He came back in 1858 with hundreds of photographs of landscapes, cities, archeologic surveys and portraits of inhabitants, and published 300 of them as L'Algérie photographiée, a three-volume in folio work.