Depending on the type of photographer you are, the Pentax 645D ($8,799.95 direct, body only)SEE IT could be a dream camera or it could be one that completely befuddles you. Event photographers can stop reading here, as the 40-megapixel camera isn't a high ISO monster, can't record video, and doesn't fire off shots in rapid succession. But if you're more of a slow shooter—whether it be studio portraits or landscapes—the weather-sealed 645D SEE IT may be right up your alley. It represents a relatively inexpensive path into medium-format digital photography, as the similar Hasselblad H4D-40 will set you back $16,995, and the Leica S2 is priced even higher at $22,995. Sports and event shooters should turn their attention to our a fast-shooting camera like the Nikon D4SEE IT, which can fire off rapid shots and capture images in even the most challenging light.

Design and Features

The 645D is big, and it's styled unlike a typical D-SLR. It has a very deep handgrip, but it's body seems squat thanks to a mirror box that extends out much further than a camera with a 35mm lens mount. The body measures 4.6 by 6.1 by 4.7 inches (HWD) and weighs in at a hefty 3 pounds, 4.2 ounces. Compare this with the Nikon D800SEE IT, a 35mm full-frame D-SLR that measures 4.8 by 5.7 by 3.2 inches and weighs only 2 pounds. Because of its weight, Pentax opted to put two tripod mounts on the body—one for portrait and one for landscape orientation—as some tripod heads won't be able to handle the camera's mass when used in a sideways position.

If you aren't familiar with what differentiates medium-format, full-frame, and APS-C, it's all about sensor size. The Pentax 645D's CCD sensor is 33 by 44mm in size, which is quite a bit larger than the 24 by 36mm sensor found on a full-frame camera like the Canon EOS 5D Mark III£1813.1 at Amazon UK, or the 18 by 24mm sensor found in a mainstream APS-C D-SLR like the Sony Alpha 77See it at Amazon UK. Because you need to cover a large physical area with light, lenses have to be bigger, as does the mirror box. 

The 645D is actually based on a lens system that captured images on 60-by-45mm frames of film, and can accept older lenses that were used with Pentax 645 film bodies. If you have the appropriate adapter, you can also mount lenses designed for the Pentax 6x7 system, capturing huge 60 by 70mm negatives on 120 or 220 format film. Aside from pure resolution, which is now available in smaller format cameras like the Nikon D800 SEE IT, there are plenty of reasons to choose medium format for your work. The larger sensor creates a different relationship between focal length and field of view. The 55mm lens that is often paired with this camera is a true normal—its focal length matches the diagonal measurement of the sensor. The equivalent focal length on a 35mm sensor camera is 43mm. This changes the distance between you and your subject, assuming that you want to maintain the same field of view, altering perspective. The larger sensor also creates a shallower depth of field than the equivalent lens on a smaller format camera, which is desirable for portraits.

If your biceps are up to it, the 645D actually handles quite well as a handheld camera, although I'd recommend using a tripod when you can. Its control layout is excellent, and there are physical control buttons, dials, and switches for almost every common function. The mode dial lets you choose standard shooting modes, there's a dedicated switch to toggle between Spot, Center Weighted, and Matrix metering, and another switch to set the focus point selection to either the center point, manual selection, or automatic operation. Because the camera's mirror is quite large, the vibration it causes when it raises to take a shot can actually cause some vibration that can hurt image quality. If your shutter speed for a shot is low and you're working on a tripod, you can utilize the Mirror Lockup feature—a toggle switch on the right side of the mirror box that causes the mirror to raise and stay raised when you first trip the shutter button. Hitting the shutter again takes the photo. If you really need to minimize vibrations, you can use this in conjunction with the Self Timer to get a rock solid shot.

Control buttons let you adjust the ISO, Exposure Compensation, Color Space, White Balance, Exposure Bracketing, and Drive Mode. There are also buttons to toggle between Raw and JPG shooting, and to select which of the two SD card slots is in use. Current shooting settings are displayed in the eye-level viewfinder, as well as on the large monochrome LCD that adorns the top of the camera—if you're shooting in a dim environment, there's a button you can press to illuminate that display as well.

There's no Live View mode on the 645D—the camera's CCD sensor technology prevents that functionality—but it didn't stop Pentax from putting an excellent 3-inch 921k-dot display on the rear of the camera, directly below the viewfinder eyecup. You can use this to configure the camera via its text-based menu system, or to review photos. The excellent resolution makes it possible to confirm focus, which is important when working with such a large image sensor, as it is less forgiving of slight focus errors.

Landscape photographers should take special note of the camera's weather sealing. Pentax designed the camera so that it could be used in inclement weather, as every port, button, and opening is sealed against the elements. When you couple this with a weather-sealed lens—there are two available at the moment—you have a camera that can shoot in a downpour, windstorm, or worse. With a little trepidation due to the replacement cost, I simulated a downpour in my kitchen sink and placed the 645D under the running water—it performed like a champ, as I was able to pick up and shoot the dripping wet camera immediately. Pentax has also released a trio of weather-sealed lenses to go along with the camera. These include the wide-angle SMC DA 645 25mm F4 AL (IF) SDM AW and the close-focusing HD D FA 645 Macro 90mm F2.8 ED AW SR. There is also a full frange of legacy lenses available in both manual focus and autofocus versions, but none of these are sealed against the elements.