The Pentax 645D, launched in March 2010 after years of development teasers, was Pentax's first digital medium format camera — a 40-megapixel machine that undercut Hasselblad and Phase One so dramatically it reshaped medium format pricing.
It houses a 40MP Kodak 44×33mm CCD sensor with no anti-aliasing filter, a weather-resistant magnesium body with over 70 seals built like an oversized K-series DSLR, dual SD card slots, an 11-point SAFOX IX+ autofocus system, a bright pentaprism finder, ISO 100-1600, and the Pentax 645AF mount taking both AF and classic manual 645 lenses.
Its significance is twofold: it made true medium format digital attainable for working landscape photographers, and its CCD sensor now enjoys the same cult reverence as the Leica M9's — a rendering devotees insist later CMOS 645Z files don't replicate. UK prices of £1.4k-£2.1k make it the cheapest route into 44×33 digital.
UK used-buying checks: ask for the shutter count (rated ~50,000 but many exceed it) and factor that Ricoh UK's repair support for the 645D is now extremely limited — a failing shutter or the known mirror-motor issue effectively totals cheap examples; test both SD slots and confirm firmware is updated for SDHC/SDXC compatibility; examine the CCD at f/16 against a bright wall for dust and, importantly, column defects or stuck pixel lines that CCDs develop; expect slow live-view-free operation and awful high ISO — that's the camera, not a fault; and check the included battery (D-LI90) and charger, both shared with the K-5/K-3 line and thankfully still available.