A man spent three hours trapped on a ledge after climbing over a barrier, ignoring warning signs, to take photos.

He was taken to Christchurch Hospital with moderate injuries after being rescued from the ledge, near the Otira Gorge Rock Shelter Lookout on the South Island's West Coast.

The viaduct is on State Highway 73, near Arthur's Pass. The lookout has a view of the Reid Falls Aqueduct.

WAIKATO WESTPAC RESCUE Two rescue helicopters were sent to Otira to rescue a man stuck on a ledge on Monday. (FILE PHOTO)

Senior Sergeant John Price said the man went to the look-out, then climbed over a barrier, past some warning signs, to take photos of the area about noon on Monday.

A Fire and Emergency New Zealand spokesman said four fire crews and two rescue helicopters went to the scene.

He said helicopter crews found it difficult to rescue the man due to the location of the ledge the man was stuck on.

An alpine cliff rescue and lines crew were called in from Christchurch. The crews dropped down to the man's location and secured him in a basket to be winched to safety.

"It's frustrating," Price said.

"This is a timely reminder to all people out walking or climbing to obey all warning signs near rock faces and cliffs – the signs are there for a reason, and if you ignore them, then this is what can happen."