u/EmbarrassedDriver662

I am going to get a 0.8x speed booster for my GFX 50S. Either the XPImage or Kipon depending on which one is cheapest when I decide to pull the trigger.

Problem is I am torn between M645 mount or Pentax 645.

Pentax 645 has the legendary 35mm 3.5, which would make a great ultrawide * 0.8.

Mamiya has the legendary 80/1.9 but I'll probably get the Mitakon 65/1.4 which is about the same when you do 80 * 0.8.

I like the Mamiya 45mm 2.8 1st gen a lot and people say the P645 45/2.8 sucks.

All in all I just don't know what system to invest in. What are everybody's experiences?