Jumping in here to offer a bit of caution before you drop your cash. Since you are rocking the S1R II, you have to be really careful about the resolving power of the glass you choose. That high-resolution sensor is pretty unforgiving. A common mistake is buying older optics that look okay on a standard body but fall apart when you try to crop in or print large. Honestly, you want something with high MTF scores or you are basically wasting that sensors potential. Also, keep an eye on the weight and balance. The S1R II is a substantial body, and some of the high-end portrait primes are massive. If the setup is too front-heavy, it can get pretty exhausting during a long session. I would also warn against focusing purely on the widest aperture if it comes at the cost of chromatic aberration. Purple fringing is a total pain to clean up on high-res portrait exports, so sometimes a well-corrected f/1.8 or f/2 is actually the smarter move for professional results. It is all about finding that balance between character and technical perfection when you have that many pixels to work with.

Hey! Still pretty new to the S1R II myself, but I've been using the Sigma 85mm f/1.4. It works! Is it the BEST? Maybe not, depends on your needs, right? But the bokeh is pretty decent, and I got it used for around $1200. Might be worth checking out some reviews first though! Just my 2 cents.