Going to be a quick post but...
You've been with said partner for around eighteen months .
He is a hobbyist/amateur photographer.
You've discovered that he has in the past, and occasionally still does, photographs and participate in porn images. (Mostly POV, or camera obviously set up on tripod).
Your partner claims you shouldn't be upset, as it's just 'acting'. He is in his late forties, all women in photos appear to be in mid twenties.
How would you deal with this? My instinct is to get away asap, or am I being a 'prude' as has been implied?