Medium format digital cameras used to be essentially film cameras fitted with digital camera backs that contained an image sensor.
In this way, professional photographers could keep using expensive gear that can cost as much as $50,000, and not have to buy a whole new system with an integrated camera back.
Then in 2010, Pentax introduced the 645D, a medium format digital camera with a fixed back. That would have cost about US$10,000 then.
The 645D could be fully weather-sealed, but still use older manual lenses as well as newer autofocus (AF) 645 system lenses. This was useful for landscape photographers who had to contend with the elements.
Now the 645D's successor, the 645Z is here. Except for minor changes, it looks much like the 645D.
But where the older model has a 40-megapixel CCD sensor, the 645Z uses a 51.4-megapixel CMOS image sensor for far better image quality. The new sensor (both are 44mm x 33mm) allows a wider sensitivity range, ISO 100 to 204,800, compared with the 645D's ISO 100 to 1,600.
The new sensor omits an optical low-pass filter that reduces moire at the expense of image sharpness. It is 1.7 times bigger than a full-frame (24mm x 36mm) image sensor and has a resulting crop factor of 0.79. So, if you use a 45mm lens with it, the actual focal length is 35.6mm.
With the SMC Pentax-FA645 45-85mm f/4.5 lens ($2,888) attached, the body weighs 2.4kg. This is certainly not a camera for the faint-hearted, especially with a price tag of $11,888 (body only).
But when you consider that many medium format digital cameras cost at least $30,000, the 645Z starts to look almost inexpensive. For photographers who find full-frame DSLRs inadequate, the 645Z offers a great upgrade option.
Another reason that this camera will suit medium format newbies is that the 645Z, though heavier and larger than a DSLR, handles much like a DSLR in that you compose pictures by looking through an eye-level optical viewfinder.
Many medium format cameras require you to compose pictures by holding the camera at waist level and looking down into the finder's glass focusing screen. Many fashion photographers prefer shooting from waist level as it allows greater interaction with the models.
The 645Z's LCD screen flips down (35 degrees) or up (125 degrees). So if you so desire, you can hold the camera at waist level and use Live View (not available in the 645D) to compose, and then shoot when you flip the display up by 90 degrees.
Built like a tank
The arrangement of buttons and controls may look confusing and intimidating at first, but it is quite logical, with front and rear command dials, and a dedicated shooting mode dial on top.
The array of rear buttons usually has more than one function, and there are four quick buttons on the top left of the body. All these buttons and controls are easily accessible to provide quick access to settings. Seasoned photographers should be able to get used to the layout without checking the manual.
The 645Z is built like a tank with its magnesium alloy exterior and aluminium die-cast chassis. The contoured rubberised grip is very deep and provides a superb grasp of the camera even if you have hands as large as the Incredible Hulk's. Handling is great. But unless you are also a seasoned weightlifter, holding the camera for extended spells will certainly hurt your wrist.
Dual SD card slots allow you to save one image in RAW and a copy in JPEG, or to use the second for extra storage.
This machine is no speed demon, but medium format models were never meant to be sports action cameras.
The 645Z takes around 1.2sec to power up and 1.9sec to shut down. Using an SD card with a writing speed of 45MB per second, the 645Z managed five RAW images in 1.6sec before the buffer ran out.
The camera has 27 autofocusing (AF) points, or 16 more than its predecessor's 11. The improvement in AF performance is evident. Using the SMC Pentax-FA645 45-85mm f/4.5 lens, AF is immediate and spot on in securing a focus under bright sunlight and in well-lit studio conditions. In low light and Live View mode, it can take 2sec to 3sec to find a focus.
Image quality is outstanding and pixel rendition is super sharp. Even with full-frame DSLRs, you will see a slight softness in lines when you zoom in. But with this camera, the RAW images are still razor sharp edge to edge when you zoom in. The JPEG images of 645Z do tend to be slightly soft, but this is easily fixed with some editing in Photoshop.
You will be amazed by the details this camera picks up. The dynamic range of the images is natural, with plenty of details preserved in the darker areas.
Colour reproduction is accurate under most circumstances, but tends to be too vivid. The camera tends to underexpose by at least a stop when it is in Aperture Priority mode and similar "auto" modes. But if you use this camera, you should be operating it in Manual mode anyway.
Noise performance is superb, with noise artefacts surfacing only at ISO 3,200. It becomes more evident at ISO 6,400 and beyond. However, significant detail loss happens only at ISO 51,200 and above, which is quite amazing.
Video is this camera's Achilles heel. While the video quality is sharp and does not pick up much ambient audio, the AF does not automatically refocus when you pan from one scene to another. You need to press the rear AF button in order to do so, and it is very slow and loud in getting the new scene sharp.
The battery is quite good, taking around 650 still images on a full charge. But the mileage will vary if you shoot RAW and JPEG at the same time.
Pound for pound, pixel for pixel, Pentax's 645Z is the best value-for-money medium format digital camera with its solid build, great handling, and superb image quality. The only question is whether you are willing to fork out $15,000 for a body and a lens?
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