Pentax 645D

Paul Burrows' full report on the Pentax 645D is below. To see all test images and specifications, download the magazine pages using the button to the right (7MB file).

Medium Well Done

The 645D set the standard for affordability in digital medium format camera systems and now the 645Z redefines it courtesy of its new CMOS sensor and next-gen processor.

In the light of what’s available in D-SLRs with full-35mm size sensors, moving up to digital medium format can be a bit hard to justify for many photographers, but it’s now more difficult to ignore because the Pentax 645Z looks like the goods on so many levels.

The original 645D was the most affordable medium format D-SLR camera on the market by a significant margin and it’s always been a bit of a mystery why Pentax wasn’t overrun by eager buyers waving credit cards… except, actually, there probably where a couple of reasons. For anybody seriously in the market for a digital medium format camera system, the 645D was severely limited because it essentially didn’t have a system… of lenses, that is. Ricoh – which now runs the Pentax show – has addressed this by making the fuller system of lenses more widely available outside Japan. So now there’s a choice of 17, including five zooms (with three more to come). That said, quite a number of these date back to the 645 film system so they lack the newer digital-era DFA-series features such as the SDM built-in focusing motors, weather-proofing and image stabilisation.

In terms of attracting users more accustomed to the luxuries of ‘APS-C’ and full-35mm D-SLRs, the 645D went a long way to closing the gap, but perhaps not far enough for some. Here the 645Z is now not only the best-featured digital medium format camera on the market – again by a significant margin – but its systems and features are comparable with the pro-level ‘APS-C’ and full-35mm format cameras currently available. It’s still more expensive that the Canon EOS-1D X and Nikon D4S – both of which blow it out of the water in terms of speed – but if the pursuit of image quality is a more important consideration then having a sensor that’s 1.7x times larger than a full-35mm imager – and in the order of 2.5x larger than ‘APS-C’ – is a good place to start.

Pentax 645D

The biggest change is the adoption of a CMOS-type sensor for the 645Z, and the significance of this is that it enables, among other things, faster continuous shooting speeds, live view and Full HD video recording. There’s a CMOS-driven revolution going on at the moment in digital medium format, mostly thanks to Sony’s development of a ‘645’ format sensor which is also being used by Hasselblad, Phase One and Mamiya Leaf in various products. All these manufacturers recognise the need to make digital medium format more attractive given the recent pace of development in the smaller formats.

However, the 645Z further builds on the major CMOS-derived performance enhancements by inheriting most of the advanced control systems and features from the Pentax K-3, Ricoh’s current ‘APS-C’ D-SLR flagship. It’s a luxury no other maker of digital medium format camera systems has, and it turns the 645Z into a truly formidable machine. OK, so it’s still quite pricey even compared with a pro-level D-SLR with a full-35mm sensor, but now that the 645Z is comparable in terms of its capabilities, it can compete more convincingly on the performance benefits of its bigger imager with its significantly higher resolution.

Pixel Power
Essentially the same device as Hasselblad uses in the H5D-50c camera and the CFV-50c capture back, and Phase One uses in its IQ150 and IQ250 backs, the 645Z’s CMOS sensor has an imaging area of 43.8x32.8 mm and a total pixel count of 52.99 megapixels (cop that, Nikon D810!). The effective pixel count is still a massive 51.4 MP which delivers a maximum image size of 8256x6192 pixels. The pixel size is 5.3 microns which helps contribute to a dynamic range of 14 stops and a native sensitivity range equivalent to ISO 100 all the way to 204,800… and that maximum is achieved without any expansion processing which is significant.

Furthermore, Pentax makes sure every drop of resolution is squeezed out of this sensor by not using a low-pass filter. Instead, the 645Z has the same ‘AA Filter Simulator’ system as the K-3 and which is a mechanical solution using sensor shifting.

Essentially working in the reverse to image stabilisation, the sensor is shifted very fractionally in order to introduce the slight blurring or ‘filtering’ needed to counter moiré patterns. There are three settings – ‘Off’ which is obviously for prioritising resolution; ‘Type 1’ which is designed to balance resolution and moiré correction by shifting the sensor in a linear direction; and ‘Type 2’ which oscillates the sensor in a circular motion in order to optimise the blurring effect and, as a result, moiré correction. The image capture options comprise JPEGs in one of four sizes and three compression levels, 14-bit RGB RAW files as either Adobe DNG or PEF, and TIFFs. RAW+JPEG capture can be configured for any JPEG size and quality setting. The new sensor is mated with Pentax’s latest-generation ‘PRIME III’ processor (as used in the K-3) which is claimed to be five times faster than the previous engine so it also helps contribute to a faster shooting speed.

OK, so 3.0 fps may not seem earth-shattering compared to the rapid-fire full-35mm D-SLRs, but it’s still fast for a digital medium format camera and nearly three times faster than the 645D. And the burst lengths are quite respectable – 30 frames with JPEG/large/best capture and ten in RAW mode.

The 645Z retains dual SD memory card slots as before, but now supports SDXC types as well as UHS-I speed data transfer plus Eye-Fi and FLU cards for wireless data transmission. The two slots can be set up in a variety of ways, including simultaneous saving to both (which creates a back-up) or the separate saving of RAW files and JPEGs. It’s also possible to copy images from one card to another.

As noted at the outset, the 645Z can also record video and it uses close to the whole sensor for this (a small outer area is reserved for electronic image stabilisation) so the depth-of-field can be even shallower than it is with a full-35mm or ‘APS-C’ which should have some video-makers drooling. It’s the first digital medium format camera with Full HD video recording.

Big Views
Another major benefit of switching to a CMOS sensor is live view, and the 645Z makes the most of this by switching from a fixed LCD monitor screen to one that’s adjustable for tilt, either up to down… which is actually a first for any Pentax D-SLR. Additionally, it’s the bigger, 8.1 cm, 3:2 aspect ratio TFT LCD panel from the K-3 with a resolution of 1.037 megadots and adjustable for brightness, colour balance and colour saturation.

Unchanged from the 645D is the optical viewfinder which employs a trapezoid-shaped pentaprism – because it’s more compact than a conventional type – and provides a 98-percent subject coverage. The standard ‘Natural Bright Matte’ focusing screen can be interchanged with one of four alternatives and it’s an easy D-I-Y procedure. Even compared to a full-35mm D-SLR, the 645Z’s viewfinder is truly huge and quickly addictive so that anything smaller starts to feel quite claustrophobic.

As with its predecessor, the 645Z looks quite imposing, but in terms of its overall bulk, it’s not vastly different from Nikon’s D4S or Canon’s EOS-1DX. The substantial handgrip is comfortable to hold, but this is definitely a two-handed camera even with one of the system’s smaller lenses fitted. The control layout is based around a main mode dial with front and rear input wheels and various function buttons. On the handgrip side these are for sensitivity, exposure compensation and the AE lock while, on the opposite side of the pentaprism housing is a line-up of four buttons for the AF area modes, instant switching to RAW capture, setting up the auto exposure bracketing and locking the rear input wheel.

Most of the top deck is taken up with a huge monochrome read-out panel which is angled towards the user. There’s a new – well, actually repurposed – selector for switching between still photography and video shooting plus, on the rear panel, a new button for either engaging live view or, in the video mode, starting and stopping recording.

The rear panel layout is actually quite similar to that of the K-3 so it’s centred around a four-way keypad which is for all navigational duties – including moving the focus point – but then each of the keys also have their own functions – providing direct access to the drive modes, white balance settings, flash modes and ‘Custom Image’ presets (more about these shortly). Pressing an adjacent button switches them between AF point duty and their other roles. As on the K-3, there’s a Status Screen display in the main monitor – showing all the main AF and AE settings – and a Control Screen which gives quick access to a range of functions for adjustment. Another option here is a dual-axis ‘artificial horizon’ level display (less intrusive bar-type level displays are provided in live view).

Taking Control
The 645Z’s bodyshell comprises all magnesium alloy covers with a total of 76 seals to protect against the intrusion of moisture or dust. Additionally, the body is insulated in key areas such as the battery compartment to enable operation to continue down to -10 degrees Celsius. Underneath is a diecast aluminium chassis and the lens mount is stainless steel.

Undoubtedly the 645D was held back by the very limited choice of lenses, but now a number of the Japan-only models have been made more widely available.

The 645Z’s control systems are essentially borrowed lock, stock and barrel from the K-3, starting with its 86,000 pixels RGB-sensitive metering sensor. In conjunction with the AF system, this delivers what Pentax calls ‘Real Time Scene Analysis’ metering which is designed to determine most appropriate metering weighting for a given subject or scene (exactly like Nikon’s ‘Scene Recognition System’). There’s the option of centre-weighted average or spot measurements.

As on the K-3, Pentax supplements the standard choice of ‘PASM’ exposure control modes with a couple of different ways of doing things. The first is Sensitivity-Priority AE – marked as ‘Sv’ on the mode dial – which allows for the ISO setting to be changed on-the-fly via the 645Z’s rear input wheel and the exposure settings are then changed accordingly.

The second is called Shutter & Aperture-Priority AE – marked ‘TAv’ on the mode dial – and it’s essentially an auto ISO control in that the ISO setting is automatically changed in order to maintain a particular combination of aperture and shutter speed as light levels vary. The program exposure mode can be customised via a selection of six aperture/speed selection lines, namely Auto, Normal, High Speed Priority, Depth-Of-Field Priority – Deep, Depth-Of-Field Priority – Shallow and MTF Priority. These are all pretty self-explanatory, but the MTF Priority setting optimises the aperture selection to match the attached lens’s MTF curve (as obtained from the lens’s CPU). Program shift is possible in all settings and with either aperture or shutter speed priority, depending on whether the front or rear input wheel is used. There’s also the option of ‘Hyper’ switching in both the program and manual modes. In program mode, turning the appropriate control wheel automatically switches the 645Z to either aperture-priority or shutter-priority auto operation… and the info display changes, for example, from ‘P’ to ‘Hyper Av’. In manual mode, pressing the ‘green-dot’ button on the camera’s back panel sets the exposure as it would be determined in the program mode and this can then be used as the starting point for fine-tuning.

The auto and semi-auto exposure control modes are backed by an AE lock, compensation up to +/-5.0 EV and auto bracketing which can be set to operate over sequences of two, three or five frames with an adjustment of up to +/-2.0 EV per frame. The 645Z’s shutter has a speed range of 30-1/4000 second and its durability has been extended to 100,000 cycles, twice the previous quoted lifespan. Flash sync is at all speeds up to 1/125 second, but the 645Z doesn’t have a built-in flash. External flash units sync via a hotshoe or a PC flash terminal.

Sharp Shooting
The autofocus system is based on the ‘SAFOX 11’ module – as introduced in the K-3 – and employs a total of 27 focusing points, 25 of them cross-type arrays arranged in a 5x5 pattern. Given the larger frame area, these cover a smaller patch than they do in the K-3, but this is still the most sophisticated AF system in the medium format world by far.

Three of the points in the very centre of the frame (arranged vertically) work with f2.8 speed lenses and the system’s the sensitivity extends down to EV -3.0 (at ISO 100). Low light assist is provided by a built-in LED illuminator. Switching between single-shot and continuous operation is done manually and there’s an extensive choice of AF area modes with auto point selection over one, nine or the full 27 points and manual point selection over one, nine, 20 or the full 27 points. In each case, the point clusters can be moved around using the navigator keypad.

Furthermore, in the Custom menu, the single-shot AF mode can be set to either focus-priority or release-priority (i.e. the shutter will still fire even if the subject isn’t in focus) while the continuous AF mode can be set to focus-priority, fps-priority or auto switching between the two. It’s also possible to determine continuous AF operation for the first frame – again focus-priority, release-priority or auto switching. Focusing tracking is supplemented with a ‘Hold AF’ adjustment – also found in the Custom menu – which has four settings from ‘Off’ to ‘High’ to vary whether the system stays locked on to the subject regardless or will refocus on a new subject, depending on the period of interruption.

In live view or when shooting video, the 645Z relies on contrast detection measurements from the sensor which often makes manual adjustment the more attractive option so, to assist here, there’s a focusing peaking display to provide assistance along with a magnified image.

The white balance control options include the ‘Multi Auto WB’ measurement which is also on the K-3, but was originally devised by Ricoh for CX Series higher-end compacts and the GXR. This employs multi-point measurement to better handle scenes which include a number of different light source, essentially by determining an average colour temperature. Additionally, the 645Z also has Pentax’s ‘Colour Temperature Enhancement’ (CTE) auto mode which increases the predominant colour in an image rather than trying to correct for it. There is a total of nine white balance presets – including four for different types of fluorescent lighting – and provisions for storing up to three custom measurements. Three manual colour temperature settings – selected from a range of 2000 to 10,000 degrees Kelvin – can also be stored. Fine-tuning in the blue-to-amber or magenta-to-green colour ranges – over a range plus/minus seven steps – is available for all the WB presets, the custom settings, the manual settings, and both the CTE and Multi Auto modes. However, as is also the case with the K-3, the 645Z doesn’t have a white balance bracketing function.

In The Picture
Also borrowed from the K-3 is a reasonable selection of options for processing JPEGs which again makes the 645Z unique in the digital medium format world where the existence of JPEGs is barely acknowledged, if at all. So the 645Z has a total of 11 ‘Custom Image’ picture presets which is one more than the K-3, due to the addition of a new one called Radiant. This joins a list that comprises Bright, Natural, Portrait, Landscape, Vibrant, Muted, Bleach Bypass, Reversal Film, Monochrome and Cross Processing.

Each of the standard colour modes is adjustable for saturation, hue, sharpness, contrast and high/low key. This last parameter varies the image brightness over a range of plus/minus four steps. Adjustments to both colour saturation and hue are made within a RGBCMY colour hexagon display which shows the variations in colour space terms.

The Bleach Bypass preset replaces the hue adjustment with a range of eight coloured toning effects (with green as the default) while the Reversal Film preset only has an adjustment for sharpness, but the colour saturation and contrast are already boosted to replicate the look of transparency film. The Cross Processing mode has a Random setting, a choice of three preset effects and provisions for storing three favourite effects.

The Monochrome ‘Custom Image’ has adjustments for sharpness, contrast and high/low key plus a set of contrast filters and a selection of toning affects. The filters are yellow, orange, red, green, magenta, blue, cyan and infrared while the toning effects range from cold-to-warm (i.e. blue-to-sepia) over plus/minus four steps. The visual effects of each preset – and any fine-tuning – can be gauged via the camera’s ‘Digital Preview’ function which captures a preview image and displays it regardless of whether live view is activated or not. This is done by flicking the power switch to a preview position (it can also be set for an optical preview… a.k.a. depth-of-field preview) and you can then chose to save this image to a card or discard it.

Creative Process
Unlike the K-3, the 645Z doesn’t have any digital filters or special effects that are available for application at the point of capture, but there’s an impressive collection of 19 available for post-capture processing.

These include the usual suspects such as Toy Camera, Retro, Miniature, Soft, Fish-Eye, Pastel, Sketch and Posterisation plus others such as Shading, Invert Colour, Unicolour Bold and Bold Monochrome. There’s also a ‘Base Parameter Adjust’ setting which enables the image’s base brightness, saturation, hue, contrast and sharpness to be fine-tuned. Incidentally, these various effects can also be appended to a RAW file and subsequently applied when the image is processed post-camera.

Multi-shot HDR capture is available and records three frames with a choice of adjustable bracketing values from +/-1.0 to +/-3.0, auto adjustment or three ‘strength’ settings called HDR1, HDR2 and HDR3. There’s also an ‘Auto Align’ correction to ensure the three frames are precisely matched. More importantly for some users, HDR capture is possible when shooting RAW – either PEF or DNG files – with the three component images saved in a single file.

Alternatively, the 645Z has dynamic range expansion processing with separate adjustments for the highlights and the shadows, both with an Auto correction option. The ‘D-Range’ corrections are performed via a combination of exposure adjustments for the highlights and an adjustment of the tone curve for the shadows.

There’s also a multiple exposure facility which can capture up to 2000 shots with the choice of three composite modes to determine the overall exposure – Average, Additive or Bright. An intervalometer also allows for up to 2000 images to be captured over intervals of two seconds up to 24 hours.

On Display
We mentioned the 645Z monitor-based info displays earlier, but it’s worth a mention here that there’s a choice of no fewer than 12 colour schemes, including – if you so desire – yellow, orange, purple or green.

The live view screen can be configured to include a real-time histogram, a highlight warning, one of five grid patterns, the bar-type electronic level displays mentioned earlier and an exposure compensation scale. The ‘Custom Image’ picture modes, white balance settings and drive modes can all be directly accessed when the camera is in live view and obviously the ‘Digital Preview’ function is available.

The image review/playback the screens include a luminance histogram superimposed over the image, a thumbnail with a full set of histograms (i.e. luminance plus the RGB channels), both highlight and shadow warnings, the grid displays and a detailed set of Exif data. The playback editing functions include cropping and resizing, basic movie editing, the ability to save a white balance setting, copying images from one memory card to the other, and a slide show function which allows for variable display times and a selection of three transitional effects. Also here is a ‘Colour Moiré Correction’ facility with three strength settings, and in-camera RAW file conversion to either a JPEG or a TIFF.

Thumbnails can be displayed in groups of six, 12, 20, 35 or 80 images, or in a ‘Calendar Filmstrip’ display. At the other end of the size scale, zoom playback allows for image  magnification of up to 16x and a ‘Quick Zoom’ function can be set to go straight to 2x, 4x, 8x or 16x . Copyright information can be added to the Exif data, namely the photographer’s name and that of the copyright holder.

Pentax carries over the menu system from its ‘APS-C’ D-SLRs to the 645Z so each chapter is divided into stand-alone pages which are individually accessed via numbered tabs (i.e. there is no continuous scrolling). Both the layout and navigation are fairly logical with repeated right-clicks delving into the sub-menus and settings, and then the ‘Menu’ button for going backwards. One ongoing idiosyncrasy is Pentax’s policy of also using the right-click key for checking some functions as well as the more logical ‘OK’ button… so, if you are in the habit of subsequently pressing ‘OK’ to confirm an action, you’ll actually end up switching that function off.

Making Movies
The idea of shooting video with a medium format D-SLR is an interesting one, but obviously the big attraction is the even shallower depth-of-field inherent in the bigger sensor compared to full-35mm. And, of course, the older manual-focus Pentax 645 film lenses aren’t an issue here either.

The 645Z records video using MPEG-4 AVC/H.264 compression in the .MOV format and, at the Full HD resolution, there’s a choice of 50 fps interlaced or 25 fps and 24 fps with progressive scan (the NTSC standard speeds are also available). For HD recording, the choice is 50 fps, 25 fps or 24 fps progressive scan. As noted in the main text, the 645Z has built-in stereo microphones with the choice of auto levels control or manual setting over a range of 20 steps. There’s also a 3.5 mm stereo audio input for connecting an external mic, but unlike on the K-3, there isn’t a stereo audio output.

The camera’s movie mode is engaged via a selector switch adjacent to the viewfinder eyepiece and there’s a recording start/stop button on the back panel. You can specify which memory card is used for storing the video clips and the functionality extends to the full set of ‘PASM’ exposure modes, continuous AF with tracking, the ‘Custom Image’ presets, dynamic range expansion processing and electronic image stabilisation. Apertures and speeds can be changed manually during recording, but not the ISO. Both the image magnification and focus peaking display are available to assist with manual focusing.

Time lapse recording is also available and at the 4K resolution of 3840x2160 pixels too (without sound obviously), but since Motion JPEG compression is used here, the resulting AVI files are huge.

Ricoh has always trod cautiously where video is concerned so it’s perhaps not surprising that the 645Z doesn’t have ‘normal’ continuous 4K shooting which would have made it really interesting… as would an uncompressed video feed to its HDMI connector and aids such as a zebra pattern generator. Consequently, the attractions of the bigger sensor aside, this is still primarily a stills camera.

Performance And Speed
With our reference memory card – Lexar’s Professional 600x 64 GB SDXC UHS-I speed device – loaded the 645Z captured a burst of 34 JPEG/large/best frames in 11.401 seconds which represents a continuous shooting speed of 2.98 fps… as near as a whisker to the quoted 3.0 fps. For the record, the average file size was 30 MB so that’s a fair amount of data to move around, but the buffer memory still emptied extremely quickly. As we found, with a UHS-I speed card, the camera will go on shooting beyond the quoted burst length, but the frame rate is reduced.

However, it’s the imaging performance that seals the deal with the Pentax 645Z… this and the fact that it’s as easy to use as any ‘small format’ D-SLR with comparable AF and metering performances. It may look imposing, but it handles beautifully and really doesn’t feel all that big in the hand (although it might with a longer lens fitted). The image quality is nothing short of stunning and, in many ways, it is just like looking at a 6x4.5cm transparency after you’ve been accustomed to 35mm. The best quality JPEGs exhibit a level of detailing that’s truly dramatic and everything stays crisply resolved even with very big enlargements (just like medium format film). Of course, it’s 51 MP resolution that’s also unfettered by an anti-aliasing filter so the amount of crisply-resolved details has to be seen to be believed.

The dynamic range is also exceptional and stays impressive even at the higher ISOs up to 6400. Noise really isn’t an issue up to ISO 3200 and even the ISO 6400 and 12,800 settings are quite useable, although some graininess is evident in areas of uniform tone. Because the 645Z is so comfortable to use hand-held, the imaging performance between ISO 100 and 1000 means you can do this in a wide range of lighting situations (which is where the TAv exposure mode really comes into its own). The settings beyond ISO 51,200 really are only there for bragging rights as they’re very noisy. Nevertheless, the 645Z still puts in a very superior high ISO performance indeed. The various ‘Custom Image’ presets provide plenty of scope for tweaking colour and sharpness when shooting JPEGs. The tonal gradations are super smooth and the subtlest of shades is handled as well as the fully saturated. There really is no aspect of the 645Z’s imaging performance that isn’t worthy of a superlative and this certainly goes some way to justifying the purchase price.

The Verdict
In the light of cameras with full-35mm sensors like Nikon’s D810 or Sony’s Alpha A7R, it can be hard to mount a compelling argument for digital medium format, but the Pentax 645Z is undoubtedly that argument. Apart from being the most affordable medium format D-SLR on the market by a long shot, it’s also the most user-friendly and the most capable, particularly if you want the convenience of shooting JPEGs. It handles as comfortably as any full-35mm D-SLR and is equally comparable in terms of its operational ease and efficiency. The reliable autofocusing operation, faster shooting speed, tiltable monitor and video capabilities also put the 645Z in a class of its own, but towering above all this is its awe-inspiring imaging quality. Here the Pentax outperforms anything with a full-35mm sensor – yes, even the D810 – yet it costs very much less than any of its rivals with 50 MP CMOS imagers.

On balance then, the Pentax 645Z simply can’t be defined by its price tag alone because this pales into insignificance in the light of everything this camera offers for that money. By that test, nothing else on the market – in any sensor format – comes close.