I started taking pictures of my partner after six months of dating. She's never been reluctant and lets me photograph her as I wish because she's aware of my needs and those of men in general. Besides, she's comfortable with her body and with nudity, so that simplifies things.
I don't think she minds me having these pictures. For her, it's mostly about feeling valued and flattering, and otherwise, she's relaxed about it.
Over time, I've accumulated several thousand! It's like an addiction !