Andrew Harris admitted possessing child pornography and child abuse material after federal police raided his home in 2019.

They found hundreds of videos and images on an iPad at the Pakenham man's home and were alerted after he posted images on a Tumblr account.

The 47-year-old "repeatedly and persistently" sought child pornography and watched hours of video of children being abused, Victorian County Court Judge Anne Hassan said on Tuesday.

"You have looked at numerous images and viewed hours of children being sexually abused for your own sexual gratification," she said.

He had viewed at least eight hours of videos involving sexual abuse of children, the judge said.

More than 100 images and videos found on the iPad were categorised among the worst categories of offending and two involved acts of sadism or bestiality.

Harris volunteered with the CFA for 30 years and was a lieutenant at Pakenham until he resigned once charges were laid.

He was awarded the Australian National Medal and National Emergency Medal for his work battling the deadly Black Saturday fires in 2009.

Though Harris started treatment for his offending, a psychologist found there was limited insight into why he was doing it, Judge Hassan said.

She labelled his conduct as "morally depraved".

However, she found the former volunteer firefighter was a good prospect for rehabilitation, was of previous good character and had no prior criminal history.

He was jailed for six months and ordered to serve a two-year community corrections order.

Australian Associated Press