This is a niche thing. It cannot be massive and publicly available. I inquired about this lens and it seems to me that this is a unique thing. The price is more than affordable, in my opinion. If you don't like it, you can buy something for 12,000 dollars. But not the fact that the pictures will be better. And you can do without an assistant who will carry your bags). Soon there will be reviews with raw files and it will be possible to say something more precisely. Evil tongues claim that the expansion margin is such that the built-in converter does not spoil the picture, moreover, you can install an additional one, the picture will still retain detail and quality. We'll see. Here is a video in English, maybe it will say something more ...