1. wire the shutter directly to the relay contacts. The drawback is the cam will take one pic when you switch from test to armed. The cam will also take a pic when the PIR goes from trip to norm (can you say backwards logic)
2. wire one side of the contact to a pull up resitor and the other side to ground. Add a N/O relay with one side of the coil connected to the contact which goes to the resistor and the other side of the coil going to ground. wire this relay's contacts to the camera shutter.
There are dozens of other ways to do it depending on whetjer you are using timers, etc.
What i have is a pir with four screws. All you have to do is put your wire in it and screw it down no soliering it has a POS, NEG, NC, and COM. IT runs off 10 to 16 volts the guy i got it from said he can get them with yhe NO on it I will call him tonight>
I'd make a guess that's some kind of Burglar Alarm PIR you got there. If someone cuts the wire coming from the relay contacts, it'd be the same as sensing movement and the Alarm would get triggered, It's called a "Closed Loop" system....
What kind of battery does that use?
Do you have a way to measure the Current of the PIR? or see it in the Spec Sheet.
Sounds like swopping out the relay may be the easiest way alright.....