First of all, I wish you the best for the Holidays, plenty of good food, happiness, and some photo shooting.
Here is quick post that includes a full resolution sample that was taken with the GFX50R + GF45 at f/2.8 and at ISO 4000. The photo was processed via C1, v11.3.1 with default noise reduction.
For the full resolution file, here is the link (I still need to figure out how to insert full resolution files within the website. Always a work in progress they say)
A few points I want to make:
(i) The GF45 has little distortion to begin with, but for this shot, I had to do some tweaks via C1 as I was not perfectly aligned with the window frame. Obviously, some resolution was a bit lost in the process but really not by much, the image still holds a 8220 x 6165 px resolution. It is important to point out that there is virtually no chromatic aberration, and also little vignetting. Fuji has not been fracking around with their GF lens lineup. I found the Canon 35 mm f/1.4 ii (one of my favorite lens, if not my favorite) to be a superb lens, but the Fujifilm GF 45mm R RW is in every aspects superior to anything I have shot with thus far.
(ii) The noise is extremely well controlled. Top class I would say. (I encourage you to download the full resolution file here)
(iii) At ISO 4000, the amount of details remains impressive. Just check the snowman at 100% view. You can even see it was MADE IN CHINA!
The Fujifilm GF50R is probably one of the best cameras (for still photography) available in the market. More importantly, it is now affordable (no need to spend 20-30k USD).