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Pentax has just announced the 645D, a 40MP medium-format digital SLR slated for release in May 2010.  The anticipated price tag of $9,400 will pale in comparison to the approximately $30,000 required to obtain a Hasselblad H4D with 40P, 50MP, or 60MP back.  I agree with Brooks Jensen that there will eventually be a limit to meaningfully noticeable improvements in image quality from digital sensor technology.  However, cameras such as the 645D demonstrate that such a ceiling remains some way off.

Traditional medium-format photography relied on shooting 6×4.5cm frames (or some variant, e.g., 6x6cm, 6x7cm) on 120 film.  This resulted in a 4:3 frame ratio (cf. the 3:2 frame ratio of 35mm).  In contrast, or in complement, the Pentax 645D features a 44x33mm CCD sensor.  All three Hasselblad H4D models also offer the same 4:3 frame ratio, albeit with larger sensors.  More importantly, these digital medium-format cameras feature sensors with 6.0μm pixels.  These are larger pixels than available in 35mm digital cameras.  Couple with the size of the medium-format sensor, such large pixel pitch should result in far larger printed images free from the negative effects of diffraction than available with the best 35mm digital SLRs.  Of course, the same could be said of prints from medium-format film versus 35mm film.

What most impresses me about cameras such as the 645D, however, is neither their sensor size nor their pixel size.  Instead, I am intrigued by the blurring of the lines within what were historically considered discrete photographic formats.  The 35mm format was once the purview of the 36x24mm frame.  The 35mm format now includes not only the relatively rare cameras with 36x24mm “full-frame” digital sensors, but also those cameras with various APS-C and APS-H crop-format sensors which preserve the original 3:2 frame ratio.  There is also the increasingly popular Four Thirds digital sensor format which offers a 4:3 frame ratio in a more compact SLR body.  The medium format was similarly restricted to the realm of the 6×4.5cm or related frame.  Yet, the medium format now includes those digital SLRs with 44.2×33.1mm, 44x33mm, 49.1×36.7mm, 53.7×40.2mm, and similar sensors.

With the rapid development of digital sensor technologies (i.e., CMOS, CCD, Foveon), it appears as if the photographic formats are each becoming varied within their ranks.  Looking back at today 10 years hence, perhaps it will be determined that the greatest benefit to photography of digital sensor technology was its ability to deconstruct the traditional boundaries of format and photographer which reigned for so many years.

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