Steven Maddock was brought back to Wolverhampton Crown Court from prison to hear Judge Michael Challinor had changed his mind.
He explained he had reflected on the matter and decided he had not given the 63-year-old married man, who was of previous good character, sufficient credit for the mitigation given to the court on his behalf and his willingness to work with probation on rehabilitation aimed at turning him away from viewing this kind of material.
Maddock's home was raided on June 30 last year after a tip off that somebody at the address was accessing an internet forum on the dark web.
A computer and external drive were among equipment seized for analysis which revealed 4,200 images of the worst kind of pornography, 3,500 from the next most serious category and 8,300 from the third classification, Mr Simon Hunka, prosecuting, told the court.
The images, featuring children aged from one to 14 years, were sorted into different files hidden behind the title of “music collection” and were so vile they left an experienced female police officer, used to having to analyse pornography, feeling “disturbed,” it was said.
Also discovered was an extreme pornographic image and 541 prohibited animated images showing torture. The defendant, a married man aged 63, had downloaded the pornography on 499 separate occasions between January 2016 and January 2018.
Mr Hunka said the offending was aggravated by the high volume of images and the age of the children together with the pain and distress they suffered.
Maddock lied when questioned, claiming that his computer had been hacked but further analysis proved this was nonsense.
Ms Samantha Powis, defending, conceded: "This was deviant behaviour and serious offending. There is a serious problem which must be addressed.
"He will engage with any expert in the field. Probation are prepared to support him but he will not receive any real help in prison.”
She suggested the answer to his “problem” may lie in his childhood which allegedly involved domestic violence from his emotionless father.
Maddock from Skip Lane, Walsall, admitted downloading and possessing obscene pornography after changing his plea to guilty a couple of weeks before his trial.
Judge Michael Challinor said at the earlier hearing: "Over 4,000 of these images were of the most serious type, not only because of the sexual violation of young children but the way in which they were restrained and assaulted in the most dreadful way.
"You are still largely in denial. You have a deviant streak in you but hopefully you can be turned away from viewing this disgusting material.”