The Cleveland Police officer also made "derogatory" remarks about the female student officer who was pictured in a "state of undress".
The man referred to as "PC A" left the force before the hearing in Hartlepool.
He had admitted two allegations about the relationship and two of breaching confidentiality in a murder case.
PC A was 38 when he entered into a sexual relationship with the probationer in her early 20s, prosecutor Stephen Morley told the disciplinary hearing.
The married officer and his junior colleague - referred to as PC X - had exchanged messages and had sex on one occasion at her home.
Mr Morley said: "PC A sent a sexual image of the female officer to another man who was not a police officer, we assume he was a friend."
The intimate photo of PC X was sent "without her knowledge" and was accompanied by "disrespectful comments" along with the remarks "probationers are class" and "she's on my shift".
Mr Morley said PC X had sent the photo to PC A "and was very upset to find he had sent it on".
PC A admitted he "was showing off to a friend of his about the sexual relationship", the panel was told.
The former officer also admitted that in early 2020, when acting as a duty sergeant, he took a picture of an internal briefing sheet about a murder suspect and sent it to his wife.
He was later convicted and fined £400 by magistrates under the Data Protection Act.
PC A had separately taken a picture and sent messages to his wife, who is not a police officer, discussing the murder and the injuries involved.
Mr Morley said: "He had sent it to her for personal reasons because him and his wife had been discussing the murder."
PC A admitted four allegations:
* Conducting a personal relationship with a junior officer
* Forwarding a personal image of a junior colleague, identifying them as a police officer and making crass, inappropriate and disrespectful comments
* Taking a photograph of confidential police information and sending it to a relative
* Being convicted of committing a criminal offence
The panel found that "the officer would've been dismissed on each and every allegation" had he not already quit.