Pentax has put a fairly aggressive cat in amongst the digital medium format pigeons and made 40 MP resolution extremely affordable, but does it have everything it needs to operate in this sector? Report by Paul Burrows.

The Pentax 645D is the most affordable medium format D-SLR on the market and is significantly cheaper than any other 40 megapixels camera system.

Digital medium format has been a bit of a graveyard for a number of brands over the last decade and you’d have to describe the current market as “challenging” so what makes Pentax think it can be profitable?

In addition to a full set of ‘PASM’ exposure control modes, the 645D also has the Sensitivity Priority AE and Aperture & Shutter Priority AE modes found on Pentax’s K-7 and K-5 ‘APS-C’ D-SLRs.

The 645D inherits the K-5’s 11-point autofocusing system which can be switched between auto or manual point selection and a ‘spot’ AF mode (which uses only the central point).

Well, for starters, it’s been here before when it launched the original Pentax 645 and, secondly, the larger format Pentax 6 x 7 (later the 67) was highly respected among pros so the brand does have form. Thirdly, Pentax has taken a proven medium format sensor design (Kodak’s ‘Truesense’ full-frame CCD platform) in a format that nicely balances resolution and pixel size, and marries it with a camera body that offers functionality and efficiencies comparable with a 35mm-based D-SLR. Fourthly, the 645D’s price is right. No wonder, then, that the established players in this market are just a teensy-weensy bit worried. No wonder too, that quite a lot of rubbish is being written about the 645D – especially on the Web – mostly by people who are unlikely to have even used the camera let alone analysed its output. There have, for example, been criticisms of the sensor’s size – 44 x 33 mm – but this is the format also used by Leaf, Phase One and Hasselblad. For the record, it’s 1.7 x larger than a 35mm-sized device. Granted it’s certainly not as big as 6 x 4.5 cm film frame (which has an imaging area of 41.5 x 56 mm in the 645NII), but then nothing in the digital medium format world is. And it’s been suggested that the Pentax’s feature suite is too ‘amateur’ in emphasis, but apart from some additional processing options for JPEGs, it’s pretty much on a par with what’s offered on the Nikon D3 series and Canon’s EOS-1D series (plus any of the semi-pro D-SLRs).

Lens Matters

If there are any issues they’re the same as those which surrounded the 645-series film cameras, namely the fixed eyelevel viewfinder and the fixed back. The former means it isn’t possible to fit a waistlevel hood, but this is also the case with the Mamiya 645AFD models (and the Phase One derivatives). The latter means it’s not possible to upgrade to a higher resolution capture device and that could be a problem for some photographers, but the plus side is that the sensor is never fully and horribly exposed as is the case when a back is detached. And, let’s be honest, 40 megapixels is going to be sufficient for a great many applications. Consequently, the biggest drawback right now is the lack of lenses optimised for digital capture and the 645D body. The lens mount is Pentax’s 645AF bayonet fitting so the digital camera will accept the earlier AF lenses from the 645N-series models as a focusing motor has been retained in the bodyshell. However, Pentax is also developing a new series of motorised SDM-series lenses of which the first is the 55mm f2.8 prime packaged locally with the 645D. This is also a weatherproofed lens, but right now it’s the only model fully optimised for use with the digital body and giving the AF performance enhancements associated with the ultrasonic drive. Automatic correction of distortion and lateral chromatic aberration can be performed with both the new D-FA series lenses and the earlier FA autofocus types. The focal length magnification factor for 6x4.5cm format lenses is 1.3x.

The total pixel count is 41.2 megapixels which is nearly double the best on offer from a 35mm D-SLR and gives a maximum image size of 7264 x 5440 pixels. Perhaps most importantly, these pixels are a healthy 6 x 6 microns in size (5.93 x 5.93 microns to be precise) which means you get ultrahigh resolution without sacrificing the signal-tonoise ratio or the dynamic range (which is quoted at a handy 11.5 stops). The laws of physics being what they are, this is only possible with a big sensor.

In terms of overall bulk, the 645D isn’t much more of a handful than an EOS-1D or D3 series DSLR. It’s on a par with any of its rivals in the 40 MP class. The basic design is that of the classic boxform medium format SLR, but with a large 35mmstyle SLR handgrip that also replicates the typical control layout of the latter. There are many visual similarities with the film cameras. When the original arrived in 1984, it introduced an unparalleled level of automation and convenience, convincing many photographers to step to the 6x4.5cm format and forcing the ‘old school’ medium format camera makers to start putting some effort into product development. Its digital descendent has the potential to do the same thing in the digital medium format camera market.