I am using the 16 mm f2.8 also. I love it for its sharpness. I shoot at F8. Anything more, diffraction occurs.
Btw, I don't think it gives u 32 megapixel on a7rz
Good to know others are using this nice little lens too.
The 32-megapixel figure comes from the resolution of the edited photo which is 6,870 x 4585 pixels = 31,498,950 pixels, or approx 32 megapixels.
The original uncropped/unedited photo's resolution is 7,360 x 4, 912 pixels = 36,152,320 pixels, or approx 36 megapixels.
I am far from being an expert with this, and it's just based on a layman's logic. I of course can be very badly mistaken, and if so, my apologies for any misinformation.