If the photo was taken with a digital camera I don't think it can be used in court, for the Photoshop reason.
A close read of the legislation, as regards proof, from IrishStatuteBook may be in order for the OP.
The ticket should give the legislation you were fined under, you could read that.
edited to add:
There is a long post on here from me, from years ago, where I got a speeding ticket. At the time a paper printout was required as proof, even though the Garda didn't have the equipment. So I challenged it in the District Court, and it was cut and dried, the legislation was very clear. The district court judge didn't agree, so I had to appeal to the Circuit Court, where the State chose not to contest the case. Not very impressive.. the State acted like a bully, as did the District Court judge.
If they had a case they would have contested it. It was a known problem. The DPP should never have allowed the case to go ahead as the Garda didn't have the required evidence.. but the DPP seemed happy to attempt to bully people too.
another edit: It's no-ones fault but our governments, that they write legislation which demands too much of the Garda.. and which the Garda can never comply with.. the problem is that the State chose to ignore this, and bully people, knowing full well that all speeding cases technically didn't have the required proof, as stated clearly in the legislation. The DPP should be independant, so I was surprised at him allowing the case to go forward.
My point is that the State might not have the required evidence to prove this case either.