Depression triggered by his teenage son's death in the Christchurch earthquake was behind a man's descent into the world of child pornography, a court has heard.

John Andrew Howland, 38, moved to the West Coast soon after the earthquake and now lives in Greymouth, where a police raid on September 25 revealed he had thousands of images of children, some just toddlers, engaged in sexual acts with adults, stored on his computer.

For the purposes of prosecution, police selected a sample of seven images as a basis for the charges, which Howland admitted in the first instance.

"Unguarded'' comments from Howland to an acquaintance had concerned that person enough to contact police.

In Greymouth District Court yesterday, lawyer Richard Bodle said Howland's curiosity developed into an obsession, but he had not produced or distributed any images.

He was what is described in the pornography scene as a 'lurker', someone who observes but does not participate in the acts.

Howland was open and co-operative with the authorities and was now seeking help for his addiction, Mr Bodle said.

Judge Paul Kellar said each charge carried a maximum sentence of five years in prison.

"This is not a victimless crime. The demand for images drives the proliferation of the production of images of the exploitation and defilement of children,'' he said.

The psychological and physical harm to the children involved was immeasurable.

The judge accepted that Howland had an entrenched addiction, was ashamed of himself, was genuine in his desire to seek help and a first time offender of prior good character.

Howland was sentenced to eight months' home detention and the judge ordered the destruction of his laptop computer.