I've been good friends with a woman from my work for about 2 years. We have lunch together 3-4 times a week. Neither of us have kids, but we enjoy talking about our husbands and our social lives.
Over some Mexican food and a margarita, somehow we ended up talking about the prevalence of porn. She mentioned that her husband is into it, and even films them on occasion. That took me by surprise. I mentioned that I'd never let my husband film me, but was curious as to why she did. She said it was just to fulfill her husband's kink. She then pulled out her phone and showed me of video of them. You couldn't see much, the camera was distant, but her writhing on the bed with her hot husband was sexy.
She said that she and her husband would like someone to film them close up. I didn't respond, so she clarified explicitly: would I film her and her husband having sex?
I said it was a weird request and I'd have to think about it. I'd never watched someone else fuck in person before. Ever. Yet her husband was hot, and I wanted to see him in action, so eventually I said yes, I'd film.
My husband would shit if he knew, but I went over to my friend's house and filmed her and her husband fucking. I was almost in the action, working the camera a few centimeters from her husband's cock and balls.
Never, at any time, did they invite me to join them, though it would have been hard to say "no" if they did. I had one hand on the camera, and one in my jeans. Seeing them fuck was hotter than I thought it would be.