Better Light has annoucned a new back coming by the end of March:
http://www.betterlight.com/super10K_PR.html
In short:
72 x 96mm capture area
10,200 x 13,600 pixels
416 Megapixels
794 MB 48-bit true RGB (no interpolation)
70 lines/mm with 60% contrast (per manufacturer specs, no tests yet)
1/8th - 1/20th of a second capture times
64 - 1000 ISO
11 resolution settings
ICC-aware
$22,995
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