7% smaller?

Given that the smallest common medium format film frames are 6cm by 4.5cm (okay, minus a couple of mm for a slide mount), and a lot of people think of proper medium format as 6cm by 6cm to 6x17cm, I think calling 45mm x 30mm "7% smaller" is pushing it a bit. "Half medium format", maybe.

The S2's an interesting (and nice) bit of kit, but looks pretty poor value compared with a Pentax 645D or the low end 'Blad back. On the other hand, compared to the going rate for the 60 to 80 MP medium format backs (that are much closer to true 645 frame size), it's a bargain. Every now and then Calumet send me a brochure proclaiming "now you too can afford a digital medium format back". Oddly, I doubt my bank manager would agree.