"I think the idea was to send a strong message to foreign and Turkish journalists who are intending to cover news in southeast Turkey," told journalists on his return to France.
Depardon was detained on 8 May in while on assignment in Hasankeyf near the Syrian border while on assignment for National Geographic magazine.
"I knew that legally I could be detained up to a year," he said.
The south-east region has seen renewed fighting between Kurdish rebels and Turkish security forces since a fragile truce collapsed in 2015.
President Recep Tayyip Erdogan's government has clamped down on press freedom in recent years, in particular since last year's failed coup.
Depardon was also accused of working without a press card - because his card was in the process of being renewed.
French President Emmanuel Macron, who last weekend asked Erdogan to ensure the journalist's return to France "as soon as possible", said in a statement: "France is committed to freedom of the press and the protection of journalists everywhere."
Depardon was deported from Turkey after living and working there for several years.