Pentax 645Z vs Sony A7R III
The Pentax 645Z and the Sony Alpha A7R III are two digital cameras that were officially introduced, respectively, in April 2014 and October 2017. The 645Z is a DSLR, while the A7R III is a mirrorless interchangeable lens camera. The cameras are based on a medium format (645Z) and a full frame (A7R III) sensor. The Pentax has a resolution of 51.1 megapixels, whereas the Sony provides 42.2 MP.
Below is an overview of the main specs of the two cameras as a starting point for the comparison.
Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax 645Z and the Sony Alpha A7R III? Which one should you buy? Read on to find out how these two cameras compare with respect to their body size, their imaging sensors, their shooting features, their input-output connections, and their reception by expert reviewers.
The side-by-side display below illustrates the physical size and weight of the Pentax 645Z and the Sony A7R III. The two cameras are presented according to their relative size. Three successive views from the front, the top, and the rear are shown. All size dimensions are rounded to the nearest millimeter.
If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Sony A7R III is considerably smaller (33 percent) than the Pentax 645Z. Moreover, the A7R III is substantially lighter (58 percent) than the 645Z. In this context, it is worth noting that both cameras are splash and dust-proof and can, hence, be used in inclement weather conditions or harsh environments.
The above size and weight comparisons are to some extent incomplete since they do not consider the interchangeable lenses that both of these cameras require. Hence, you might want to study and compare the specifications of available lenses in order to get the full picture of the size and weight of the two camera systems.
The power pack in the A7R III can be charged via the USB port, which can be very convenient when travelling.
The following table provides a synthesis of the main physical specifications of the two cameras and other similar ones. In case you want to display and compare another camera duo, you can use the CAM-parator app to select your camera combination among a large number of options.
|Pentax 645Z||6.1 in||4.6 in||4.8 in||54.7 oz||650||Y||Apr 2014||8,499|
|Sony A7R III||5.0 in||3.8 in||2.9 in||22.9 oz||650||Y||Oct 2017||3,199|
|Canon 1D X Mark II||6.2 in||6.6 in||3.3 in||54.0 oz||1210||Y||Feb 2016||5,999|
|Canon 5DS||6.0 in||4.6 in||3.0 in||32.8 oz||700||Y||Feb 2015||3,699|
|Canon 5DS R||6.0 in||4.6 in||3.0 in||32.8 oz||700||Y||Feb 2015||3,699|
|Hasselblad X1D||5.9 in||3.9 in||2.8 in||25.6 oz||..||Y||Jun 2016||8,995|
|Leica SL||5.8 in||4.1 in||1.5 in||29.9 oz||400||Y||Oct 2015||7,450|
|Nikon Z7||5.3 in||4.0 in||2.6 in||23.8 oz||330||Y||Aug 2018||3,399|
|Nikon D850||5.7 in||4.9 in||3.1 in||35.5 oz||1840||Y||Jul 2017||3,299|
|Nikon D5||6.3 in||6.3 in||3.6 in||49.9 oz||3780||Y||Jan 2016||6,499|
|Nikon D7200||5.4 in||4.2 in||3.0 in||27.0 oz||1110||Y||Mar 2015||1,199|
|Nikon D4S||6.3 in||6.2 in||3.6 in||47.6 oz||3020||Y||Feb 2014||6,499|
|Pentax 645D||6.1 in||4.6 in||4.7 in||52.2 oz||800||Y||Mar 2010||9,995|
|Sony A9||5.0 in||3.8 in||2.5 in||23.7 oz||650||Y||Apr 2017||4,499|
|Sony A99 II||5.6 in||4.1 in||3.0 in||29.9 oz||490||Y||Sep 2016||3,199|
|Sony A7R II||5.0 in||3.8 in||2.4 in||22.0 oz||290||Y||Jun 2015||3,199|
|Sony A7S II||5.0 in||3.8 in||2.4 in||22.1 oz||370||Y||Sep 2015||2,999|
|Notes: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.|
The price is, of course, an important factor in any camera decision. The manufacturer’s suggested retail prices give an idea on the placement of the camera in the maker’s lineup and the broader market. The A7R III was launched at a markedly lower price (by 62 percent) than the 645Z, which puts it into a different market segment. Usually, retail prices stay at first close to the launch price, but after several months, discounts become available. Later in the product cycle and, in particular, when the replacement model is about to appear, further discounting and stock clearance sales often push the camera price considerably down.
The imaging sensor is at the core of digital cameras and its size is one of the main determining factors of image quality. All other things equal, a large sensor will have larger individual pixel-units that offer better low-light sensitivity, wider dynamic range, and richer color-depth than smaller pixels in a sensor of the same technological generation. Further, a large sensor camera will give the photographer additional creative options when using shallow depth-of-field to isolate a subject from its background. On the downside, larger sensors tend to be more expensive and lead to bigger and heavier cameras and lenses.
Of the two cameras under consideration, the Pentax 645Z features a medium format sensor and the Sony A7R III a full frame sensor. The sensor area in the A7R III is 40 percent smaller. As a result of these sensor size differences, the cameras have a format factor of, respectively, 0.79 and 1.0. The sensor in the 645Z has a native 4:3 aspect ratio, while the one in the A7R III offers a 3:2 aspect.
With 51.1MP, the 645Z offers a higher resolution than the A7R III (42.2MP), but the 645Z nevertheless has larger individual pixels (pixel pitch of 5.30μm versus 4.52μm for the A7R III) due to its larger sensor. However, the A7R III is a much more recent model (by 3 years and 6 months) than the 645Z, and its sensor will have benefitted from technological advances during this time that further enhance the light gathering capacity of its pixels. Coming back to sensor resolution, it should be mentioned that neither of the two cameras has an anti-alias filter installed, so they are able to capture all the detail the sensor resolves.
The resolution advantage of the Pentax 645Z implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the 645Z for good quality output (200 dots per inch) amounts to 41.3 x 31 inches or 104.9 x 78.6 cm, for very good quality (250 dpi) 33 x 24.8 inches or 83.9 x 62.9 cm, and for excellent quality (300 dpi) 27.5 x 20.6 inches or 69.9 x 52.4 cm. The corresponding values for the Sony A7R III are 39.8 x 26.5 inches or 101 x 67.4 cm for good quality, 31.8 x 21.2 inches or 80.8 x 53.9 cm for very good quality, and 26.5 x 17.7 inches or 67.3 x 44.9 cm for excellent quality prints.
The A7R III has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.
Unlike the 645Z, the A7R III has the capacity to capture high quality composite images by combining multiple shots after shifting its sensor by miniscule distances. This multi-shot, pixel-shift mode is most suitable for photography of stationary objects (landscapes, studio scenes).
The Pentax 645Z has a native sensitivity range from ISO 100 to ISO 204800. The corresponding ISO settings for the Sony Alpha A7R III are ISO 100 to ISO 32000, with the possibility to increase the ISO range to 50-102400.
For many cameras, data on sensor performance has been reported by DXO Mark. This service assesses and scores the color depth ("DXO Portrait"), dynamic range ("DXO Landscape"), and low-light sensitivity ("DXO Sports") of camera sensors, and also publishes an overall camera score. The Overall DXO ratings for the two cameras under consideration are close, suggesting that they provide similar imaging performance. The following table provides an overview of the physical sensor characteristics, as well as the sensor quality measurements for a selection of comparators.
| DXO |
|Pentax 645Z||Medium Format||51.1||8256||6192||1080/60i||26.0||14.7||4505||101|
|Sony A7R III||Full Frame||42.2||7952||5304||4K/30p||26.0||14.7||3523||100|
|Canon 1D X Mark II||Full Frame||20.0||5472||3648||4K/60p||24.1||13.5||3207||88|
|Canon 5DS||Full Frame||50.3||8688||5792||1080/30p||24.7||12.4||2381||87|
|Canon 5DS R||Full Frame||50.3||8688||5792||1080/30p||24.6||12.4||2308||86|
|Hasselblad X1D||Medium Format||51.3||8272||6200||1080/25p||26.2||14.8||4489||102|
|Leica SL||Full Frame||24.0||6000||4000||4K/30p||25.0||13.4||1821||88|
|Nikon Z7||Full Frame||45.4||8256||5504||4K/30p||26.3||14.6||2668||99|
|Nikon D850||Full Frame||45.4||8256||5504||4K/30p||26.4||14.8||2660||100|
|Nikon D5||Full Frame||20.7||5588||3712||4K/30p||25.1||12.3||2343||88|
|Nikon D4S||Full Frame||16.2||4928||3280||1080/60p||24.4||13.3||3074||89|
|Pentax 645D||Medium Format||39.5||7264||5440||none||24.6||12.6||1262||82|
|Sony A9||Full Frame||24.0||6000||4000||4K/30p||24.9||13.3||3517||92|
|Sony A99 II||Full Frame||42.2||7952||5304||4K/30p||25.4||13.4||2317||92|
|Sony A7R II||Full Frame||42.2||7952||5304||4K/30p||26.0||13.9||3434||98|
|Sony A7S II||Full Frame||12.0||4240||2832||4K/30p||23.6||13.3||2993||85|
Many modern cameras cannot only take still pictures, but also record videos. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the A7R III provides a better video resolution than the 645Z. It can shoot movie footage at 4K/30p, while the Pentax is limited to 1080/60i.
Apart from body and sensor, cameras can and do differ across a range of features. For example, the A7R III has an electronic viewfinder (3686k dots), while the 645Z has an optical one. Both systems have their advantages, with the electronic viewfinder making it possible to project supplementary shooting information into the framing view, whereas the optical viewfinder offers lag-free viewing and a very clear framing image. The viewfinders of both cameras offer the same magnification (0.78x), but the one in the A7R III has a wider field of view (100%) than the finder in the 645Z (98%), so that a larger proportion of the captured image is visible. The table below summarizes some of the other core capabilities of the Pentax 645Z and Sony A7R III in connection with corresponding information for a sample of similar cameras.
|Sony A7R III||3686||n||3.0||1440||tilting||Y||1/8000s||10.0||n||Y|
|Canon 1D X Mark II||optical||Y||3.2||1620||fixed||Y||1/8000s||16.0||n||n|
|Canon 5DS R||optical||Y||3.2||1040||fixed||n||1/8000s||5.0||n||n|
|Sony A99 II||2400||Y||3.0||1229||full-flex||n||1/8000s||12.0||n||Y|
|Sony A7R II||2400||n||3.0||1229||tilting||n||1/8000s||5.0||n||Y|
|Sony A7S II||2400||n||3.0||1229||tilting||n||1/8000s||5.0||n||Y|
One feature that is present on the 645Z, but is missing on the A7R III is a top-level LCD. While being, of course, smaller than the rear screen, the control panel conveys some of the essential shooting information and can be convenient for quick and easy settings verification.
The reported shutter speed information refers to the use of the mechanical shutter. Yet, some cameras only have an electronic shutter, while others have an electronic shutter in addition to a mechanical one. In fact, the A7R III is one of those camera that have an additional electronic shutter, which makes completely silent shooting possible. However, this mode is less suitable for photographing moving objects (risk of rolling shutter) or shooting under artificial light sources (risk of flickering).
The Pentax 645Z and the Sony A7R III both have an intervalometer built-in. This enables the photographer to capture time lapse sequences, such as flower blooming, a sunset or moon rise, without purchasing an external camera trigger and related software.
The 645Z writes its imaging data to SDXC cards, while the A7R III uses SDXC or Memory Stick PRO Duo cards. Both cameras feature dual card slots, which can be very useful in case a memory card fails. The A7R III supports UHS-II cards (on its first slot), while the 645Z can use UHS-I cards.
For some imaging applications, the extent to which a camera can communicate with its environment can be an important aspect in the camera decision process. The table below provides an overview of the connectivity of the Pentax 645Z and Sony Alpha A7R III and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.
| WiFi |
| NFC |
|Sony A7R III||Y||stereo||mono||Y||Y||micro||3.1||Y||Y||Y|
|Canon 1D X Mark II||Y||mono||mono||Y||Y||mini||3.0||-||-||-|
|Canon 5DS R||Y||mono||mono||Y||-||mini||3.0||-||-||-|
|Sony A99 II||Y||stereo||mono||Y||Y||micro||2.0||Y||Y||Y|
|Sony A7R II||Y||stereo||mono||Y||Y||micro||2.0||Y||Y||-|
|Sony A7S II||Y||stereo||mono||Y||Y||micro||2.0||Y||Y||-|
It is notable that the A7R III offers wifi support, which can be a very convenient means to transfer image data to an off-camera location. In contrast, the 645Z does not provide wifi capability.
Both cameras feature a PC Sync terminal to control professional strobe lights, which will be appreciated by studio photographers.
The 645Z is a recent model that features in the current product line-up of Pentax. In contrast, the A7R III has been discontinued (but can be found pre-owned on eBay). As a replacement in the same line of cameras, the A7R III was succeeded by the Sony A7R IV. Further information on the two cameras (e.g. user guides, manuals), as well as related accessories, can be found on the official Pentax and Sony websites.
So what conclusions can be drawn? Is the Pentax 645Z better than the Sony A7R III or vice versa? The listing below highlights the relative strengths of the two models.
Advantages of the Pentax 645Z:
- More detail: Offers more megapixels (51.1 vs 42.2MP) with a 8% higher linear resolution.
- Better low-light sensitivity: Requires less light for good images (0.4 stops ISO advantage).
- Brighter framing: Features an optical viewfinder for clear, lag-free composition.
- Easier setting verification: Features an LCD display on top to control shooting parameters.
- Larger screen: Has a bigger rear LCD (3.2" vs 3.0") for image review and settings control.
- More heavily discounted: Has been available for much longer (launched in April 2014).
Reasons to prefer the Sony Alpha A7R III:
- High quality composites: Can combine several shots after pixel-shifting its sensor.
- Better video: Provides higher definition movie capture (4K/30p vs 1080/60i).
- Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
- Better sound control: Has a headphone port that enables audio monitoring while recording.
- More framing info: Has an electronic viewfinder that displays shooting data.
- More complete view: Has a viewfinder with a larger field of view (100% vs 98%).
- More detailed LCD: Has a higher resolution rear screen (1440k vs 1037k dots).
- Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
- Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/4000s) to freeze action.
- Faster burst: Shoots at higher frequency (10 vs 3 flaps/sec) to capture the decisive moment.
- Less disturbing: Has an electronic shutter option for completely silent shooting.
- More compact: Is smaller (127x96mm vs 156x117mm) and will fit more readily into a bag.
- Less heavy: Has a lower weight (by 900g or 58 percent) and is thus easier to take along.
- Easier travel charging: Can be conveniently charged via its USB port.
- Sharper images: Has stabilization technology built-in to reduce the impact of hand-shake.
- More legacy lens friendly: Can use many non-native lenses via adapters.
- Easier file upload: Has wifi built in for automatic backup or image transfer to the web.
- Easier device pairing: Supports NFC for fast wireless image transfer over short distances.
- Easier wireless transfer: Supports Bluetooth for image sharing without cables.
- Faster buffer clearing: Supports a more advanced SD data transfer standard (UHS-II vs UHS-I).
- More affordable: Was introduced into a lower priced category (62 percent cheaper at launch).
- More modern: Reflects 3 years and 6 months of technical progress since the 645Z launch.
If the number of relative strengths (bullet points above) is taken as a guide, the A7R III is the clear winner of the contest (23 : 6 points). However, the relative importance of the various individual camera aspects will vary according to personal preferences and needs, so that you might like to apply corresponding weights to the particular features before making a decision on a new camera. A professional wedding photographer will view the differences between cameras in a way that diverges from the perspective of a travel photog, and a person interested in cityscapes has distinct needs from a macro shooter. Hence, the decision which camera is best and worth buying is often a very personal one.
How about other alternatives? Do the specifications of the Pentax 645Z and the Sony A7R III place the cameras among the top in their class? Find out in the latest Best DSLR Camera and Best Mirrorless Interchangeable Lens Camera listings whether the two cameras rank among the cream of the crop.
In any case, while the comparison of technical specifications can provide a useful overview of the capabilities of different cameras, it remains incomplete and does no justice, for example, to the way the 645Z or the A7R III perform in practice. User reviews, such as those found at amazon, can sometimes inform about these issues, but such feedback is often incomplete, inconsistent, and biased.
This is why hands-on reviews by experts are important. The following table reports the overall ratings of the cameras as published by some of the major camera review sites (cameralabs, dpreview, ephotozine, imaging-resource, and photographyblog). As can be seen, the professional reviewers agree in many cases on the quality of different cameras, but sometimes their assessments diverge, reinforcing the earlier point that a camera decision is often a very personal choice.
|Pentax 645Z||..||..||4.5/5||5/5||5/5||Apr 2014||8,499|
|Sony A7R III||+ +||90/100||4.5/5||5/5||5/5||Oct 2017||3,199|
|Canon 1D X Mark II||..||89/100||4.5/5||5/5||4.5/5||Feb 2016||5,999|
|Canon 5DS||+||83/100||4.5/5||5/5||4.5/5||Feb 2015||3,699|
|Canon 5DS R||+||83/100||5/5||5/5||4.5/5||Feb 2015||3,699|
|Hasselblad X1D||o||81/100||..||..||4/5||Jun 2016||8,995|
|Leica SL||..||84/100||4.5/5||4/5||4/5||Oct 2015||7,450|
|Nikon Z7||+||89/100||4.5/5||4.5/5||5/5||Aug 2018||3,399|
|Nikon D850||+ +||89/100||4.5/5||5/5||5/5||Jul 2017||3,299|
|Nikon D5||..||89/100||4.5/5||5/5||5/5||Jan 2016||6,499|
|Nikon D7200||+ +||84/100||4.5/5||4/5||4.5/5||Mar 2015||1,199|
|Nikon D4S||..||..||4.5/5||5/5||4.5/5||Feb 2014||6,499|
|Pentax 645D||..||..||..||4.5/5||..||Mar 2010||9,995|
|Sony A9||+ +||89/100||5/5||5/5||5/5||Apr 2017||4,499|
|Sony A99 II||..||85/100||4.5/5||4.5/5||4.5/5||Sep 2016||3,199|
|Sony A7R II||+ +||90/100||5/5||4.5/5||5/5||Jun 2015||3,199|
|Sony A7S II||+||..||4.5/5||5/5||5/5||Sep 2015||2,999|
|Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.|
The above review scores should be interpreted with care, though. The ratings are only valid when referring to cameras in the same category and of the same age. A score, therefore, has to be seen in close connection to the price and market introduction time of the camera, and comparisons of ratings among very different cameras or across long time periods have little meaning. It should also be noted that some of the review sites have over time altered the way they render their verdicts.
Other camera comparisons
Did this review help to inform your camera decision process? If you would like to see a different side-by-side camera review, just use the search menu below. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.
Specifications: Pentax 645Z vs Sony A7R III
Below is a side-by-side comparison of the specs of the two cameras to facilitate a quick review of their differences and common features.
|Camera Model||Pentax 645Z||Sony A7R III|
|Camera Type||Digital single lens reflex||Mirrorless system camera|
|Camera Lens||Pentax 645 mount lenses||Sony E mount lenses|
|Launch Date||April 2014||October 2017|
|Launch Price||USD 8,499||USD 3,199|
|Sensor Specs||Pentax 645Z||Sony A7R III|
|Sensor Format||Medium Format Sensor||Full Frame Sensor|
|Sensor Size||43.8 x 32.8 mm||35.9 x 24.0 mm|
|Sensor Area||1436.64 mm2||861.6 mm2|
|Sensor Diagonal||54.7 mm||43.2 mm|
|Sensor Resolution||51.1 Megapixels||42.2 Megapixels|
|Image Resolution||8256 x 6192 pixels||7952 x 5304 pixels|
|Pixel Pitch||5.30 μm||4.52 μm|
|Pixel Density||3.56 MP/cm2||4.90 MP/cm2|
|Moiré control||no AA filter||no AA filter|
|Movie Capability||1080/60i Video||4K/30p Video|
|ISO Setting||100 - 204,800 ISO||100 - 32,000 ISO|
|ISO Boost||no Enhancement||50 - 102,400 ISO|
|Image Processor||PRIME III||BIONZ X|
|DXO Sensor Quality (score)||101||100|
|DXO Color Depth (bits)||26.0||26.0|
|DXO Dynamic Range (EV)||14.7||14.7|
|DXO Low Light (ISO)||4505||3523|
|Screen Specs||Pentax 645Z||Sony A7R III|
|Viewfinder Type||Optical viewfinder||Electronic viewfinder|
|Viewfinder Field of View||98%||100%|
|Viewfinder Resolution||3686k dots|
|Top-Level Screen||Control Panel||no Top Display|
|LCD Framing||Live View||Live View|
|Rear LCD Size||3.2inch||3.0inch|
|LCD Resolution||1037k dots||1440k dots|
|LCD Attachment||Tilting screen||Tilting screen|
|Touch Input||no Touchscreen||Touchscreen|
|Shooting Specs||Pentax 645Z||Sony A7R III|
|Focus System||Phase-detect AF||On-Sensor Phase-detect|
|Manual Focusing Aid||Focus Peaking||Focus Peaking|
|Max Shutter Speed (mechanical)||1/4000s||1/8000s|
|Continuous Shooting||3 shutter flaps/s||10 shutter flaps/s|
|Shutter Life Expectancy||100 000 actuations||500 000 actuations|
|Electronic Shutter||no E-Shutter||YES|
|Time-Lapse Photography||Intervalometer built-in||Intervalometer built-in|
|Image Stabilization||Lens stabilization only||In-body stabilization|
|Fill Flash||no On-Board Flash||no On-Board Flash|
|Storage Medium||SDXC cards||MS or SDXC cards|
|Second Storage Option||Dual card slots||Dual card slots|
|UHS card support||UHS-I||Single UHS-II|
|Connectivity Specs||Pentax 645Z||Sony A7R III|
|Studio Flash||PC Sync socket||PC Sync socket|
|USB Connector||USB 3.0||USB 3.1|
|HDMI Port||mini HDMI||micro HDMI|
|Microphone Port||External MIC port||External MIC port|
|Headphone Socket||no Headphone port||Headphone port|
|Wifi Support||no Wifi||Wifi built-in|
|Near-Field Communication||no NFC||NFC built-in|
|Bluetooth Support||no Bluetooth||Bluetooth built-in|
|Body Specs||Pentax 645Z||Sony A7R III|
|Environmental Sealing||Weathersealed body||Weathersealed body|
|Battery Life (CIPA)||650 shots per charge||650 shots per charge|
|In-Camera Charging||no USB charging||USB charging|
156 x 117 x 123 mm
(6.1 x 4.6 x 4.8 in)
127 x 96 x 74 mm
(5.0 x 3.8 x 2.9 in)
|Camera Weight||1550 g (54.7 oz)||650 g (22.9 oz)|
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