Inaccessible in terms of cost of large sensors, and inaccessible in terms of getting the same format size for which the equipment (especially the lens) was designed. Apart from prohibitively expensive scanning backs, I am not aware of any fixed sensor that covers the full 6x7, 4x5, 8x10 etc size. There are many alternatives in various sizes. But my point is that for the vast majority of MF and LF cameras and lenses, no feasible digital extension exists which staves off their obsoletion. Even my Mamiya 645 AFD II, which is nominally digital-ready, is hampered by lack of an affordable sensor that covers the 42x56 frame size. That is what I meant by inaccessible. Not as in "NASA can't do it" but as in "Ordinary Joe can't do it".
Originally Posted by analoguey