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Pentax 645Z versus 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 megapixel, whereas the Sony provides 42.2 MP. Read on to find out how these two cameras compare with respect to their size, their sensors, their features, and their reception by expert reviewers.

Body comparison: Pentax 645Z vs Sony A7R III

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. You can also toggle the display to switch to a percentage comparison if you prefer that the measures are being expressed in relative terms (in this case, the camera on the left – the 645Z – represents the basis or 100 percent across all the size and weight measures).

Compare Pentax 645Z vs Sony A7R III
Compare 645Z versus A7R III top
Compare 645Z and A7R III rear

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 the specifications of available lenses in order to get the full picture of the size and weight of the two camera systems.

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, just click on the right or left arrow next to the camera that you would like to inspect. Alternatively, you can also use the CAM-parator to select your camera combination among a larger number of options.

Camera Body Specifications
  Camera
Model
Camera
Width
Camera
Height
Camera
Depth
Camera
Weight
Battery
Life
(CIPA)
Weather
Sealing
(yes/no)
Camera
Launch
(announced)
Launch
Price
(USD)
Street
Price
(USD)
Used
Price
(USD)
Camera
Model
Pentax 645Z» 6.1 in 4.6 in 4.8 in 54.7 oz 650 Y Apr 2014 8,499 i i Pentax 645Z
Sony A7R III« 5.0 in 3.8 in 2.9 in 22.9 oz 650 Y Oct 2017 3,199 i i Sony A7R III
Canon 1D X Mark II« » 6.2 in 6.6 in 3.3 in 54.0 oz 1210 Y Feb 2016 5,999 i i Canon 1D X Mark II
Canon 5DS« » 6.0 in 4.6 in 3.0 in 32.8 oz 700 Y Feb 2015 3,699 i i Canon 5DS
Canon 5DS R« » 6.0 in 4.6 in 3.0 in 32.8 oz 700 Y Feb 2015 3,699 i i Canon 5DS R
Hasselblad X1D« » 5.9 in 3.9 in 2.8 in 25.6 oz .. Y Jun 2016 8,995 i i Hasselblad X1D
Leica SL« » 5.8 in 4.1 in 1.5 in 29.9 oz 400 Y Oct 2015 7,450 i i Leica SL
Nikon D850« » 5.7 in 4.9 in 3.1 in 35.5 oz 1840 Y Jul 2017 3,299 i i Nikon D850
Nikon D5« » 6.3 in 6.3 in 3.6 in 49.9 oz 3780 Y Jan 2016 6,499 i i Nikon D5
Nikon D7200« » 5.4 in 4.2 in 3.0 in 27.0 oz 1110 Y Mar 2015 1,199- i Nikon D7200
Nikon D4S« » 6.3 in 6.2 in 3.6 in 47.6 oz 3020 Y Feb 2014 6,499- i Nikon D4S
Pentax 645D« » 6.1 in 4.6 in 4.7 in 52.2 oz 800 Y Mar 2010 9,995- i Pentax 645D
Sony A7 III« » 5.0 in 3.8 in 2.9 in 22.9 oz 610 Y Feb 2018 1,999 i i Sony A7 III
Sony A9« » 5.0 in 3.8 in 2.5 in 23.7 oz 650 Y Apr 2017 4,499 i i Sony A9
Sony A99 II« » 5.6 in 4.1 in 3.0 in 29.9 oz 490 Y Sep 2016 3,199 i i Sony A99 II
Sony A7R II« » 5.0 in 3.8 in 2.4 in 22.0 oz 290 Y Jun 2015 3,199- i Sony A7R II
Sony A7S II« » 5.0 in 3.8 in 2.4 in 22.1 oz 370 Y Sep 2015 2,999 i i Sony A7S II

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.

 

Sensor comparison: Pentax 645Z vs Sony A7R III

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.

Pentax 645Z and Sony A7R III sensor measures

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 somewhat more recent model (by 3 years and 6 months) than the 645Z, and its sensor might 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 A7R III has on-sensor phase detect pixels, which results in relatively fast and reliable autofocus acquisition during video recording.

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).

645Z versus A7R III MP

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 image quality. The following table provides an overview of the physical sensor characteristics, as well as the sensor quality measurements for a selection of comparators.

Sensor Characteristics
  Camera
Model
Sensor
Class
Resolution
(MP)
Horiz.
Pixels
Vert.
Pixels
Video
Format
DXO
Portrait
DXO
Landscape
DXO
Sports
DXO
Overall
Camera
Model
Pentax 645Z» Medium Format 51.1 8256 61921080/60i26.014.74505101Pentax 645Z
Sony A7R III« Full Frame 42.2 7952 53044K/30p26.014.73523100Sony A7R III
Canon 1D X Mark II« » Full Frame 20.0 5472 36484K/60p24.113.5320788Canon 1D X Mark II
Canon 5DS« » Full Frame 50.3 8688 57921080/60p24.712.4238187Canon 5DS
Canon 5DS R« » Full Frame 50.3 8688 57921080/60p24.612.4230886Canon 5DS R
Hasselblad X1D« » Medium Format 51.3 8272 62001080/25p26.214.84489102Hasselblad X1D
Leica SL« » Full Frame 24.0 6000 40004K/30p25.013.4182188Leica SL
Nikon D850« » Full Frame 45.4 8256 55044K/30p26.414.82660100Nikon D850
Nikon D5« » Full Frame 20.7 5588 37124K/30p25.112.3234388Nikon D5
Nikon D7200« » APS-C 24.0 6000 40001080/60p24.514.6133387Nikon D7200
Nikon D4S« » Full Frame 16.2 4928 32801080/60p24.413.3307489Nikon D4S
Pentax 645D« » Medium Format 39.5 7264 5440-24.612.6126282Pentax 645D
Sony A7 III« » Full Frame 24.0 6000 40004K/30p25.014.7373096Sony A7 III
Sony A9« » Full Frame 24.0 6000 40004K/30p24.913.3351792Sony A9
Sony A99 II« » Full Frame 42.2 7952 53044K/30p25.413.4231792Sony A99 II
Sony A7R II« » Full Frame 42.2 7952 53044K/30p26.013.9343498Sony A7R II
Sony A7S II« » Full Frame 12.0 4240 28324K/30p23.613.3299385Sony A7S II

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.

 

Feature comparison: Pentax 645Z vs Sony A7R III

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 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. If you need more detail on the specs, you can find comprehensive listings, for example, in the dpreview camera hub.

Core Features
  Camera
Model
Viewfinder
(Type or
'000 dots)
Control
Panel
(yes/no)
LCD
Size
(inch)
LCD
Resolution
('000 dots)
LCD
Attach-
ment
Touch
Screen
(yes/no)
Shutter
speed
(1/sec)
Shutter
flaps
(1/sec)
Build-in
Flash
(yes/no)
Build-in
Image
Stab
Camera
Model
Pentax 645Z»optical Y 3.2 1037 tilting n 4000 3.0 n n Pentax 645Z
Sony A7R III«3686 n 3.0 1440 tilting Y 8000 10.0 n Y Sony A7R III
Canon 1D X Mark II« »optical Y 3.2 1620 fixed Y 8000 16.0 n n Canon 1D X Mark II
Canon 5DS« »optical Y 3.2 1040 fixed n 8000 5.0 n n Canon 5DS
Canon 5DS R« »optical Y 3.2 1040 fixed n 8000 5.0 n n Canon 5DS R
Hasselblad X1D« »2360 n 3.0 920 fixed Y 2000 2.3 n n Hasselblad X1D
Leica SL« »4400 Y 3.0 1040 fixed Y 8000 11.0 n n Leica SL
Nikon D850« »optical Y 3.2 2359 tilting Y 8000 9.0 n n Nikon D850
Nikon D5« »optical Y 3.2 2359 fixed Y 8000 14.0 n n Nikon D5
Nikon D7200« »optical Y 3.2 1229 fixed n 8000 6.0 Y n Nikon D7200
Nikon D4S« »optical Y 3.2 921 fixed n 8000 11.0 n n Nikon D4S
Pentax 645D« »optical Y 3.0 921 fixed n 4000 1.1 n n Pentax 645D
Sony A7 III« »2359 n 3.0 922 tilting Y 8000 10.0 n Y Sony A7 III
Sony A9« »3686 n 3.0 1440 tilting Y 8000 20.0 n Y Sony A9
Sony A99 II« »2400 Y 3.0 1229 full-flex n 8000 12.0 n Y Sony A99 II
Sony A7R II« »2400 n 3.0 1229 tilting n 8000 5.0 n Y Sony A7R II
Sony A7S II« »2400 n 3.0 1229 tilting n 8000 5.0 n Y Sony A7S II

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 and shutter burst refer to the use of the mechanical shutter. In addition, the A7R III features an electronic shutter, which makes completely silent shooting possible. However, this mode is less suitable for photographing moving objects (rolling shutter) or shooting under artificial light sources (flickering).

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.

Input-Output Connections
  Camera
Model
Hotshoe
Port
Internal
Microphone
Internal
Speaker
Microphone
Port
Headphone
Port
HDMI
Port
USB
Type
WiFi
Support
NFC
Support
Bluetooth
Support
Camera
Model
Pentax 645Z»YstereomonoY-mini3.0---Pentax 645Z
Sony A7R III«YstereomonoYYmicro3.1YYYSony A7R III
Canon 1D X Mark II« »YmonomonoYYmini3.0---Canon 1D X Mark II
Canon 5DS« »YmonomonoY-mini3.0---Canon 5DS
Canon 5DS R« »YmonomonoY-mini3.0---Canon 5DS R
Hasselblad X1D« »YstereomonoYYmini3.0Y--Hasselblad X1D
Leica SL« »YstereomonoYYfull3.0Y--Leica SL
Nikon D850« »YstereomonoYYmini3.0YYYNikon D850
Nikon D5« »YstereomonoYYmini3.0---Nikon D5
Nikon D7200« »YstereomonoYYmini2.0YY-Nikon D7200
Nikon D4S« »YmonomonoYYmini2.0---Nikon D4S
Pentax 645D« »Ystereo----2.0---Pentax 645D
Sony A7 III« »YstereomonoYYmicro3.1YYYSony A7 III
Sony A9« »YstereomonoYYmicro2.0YYYSony A9
Sony A99 II« »YstereomonoYYmicro2.0YYYSony A99 II
Sony A7R II« »YstereomonoYYmicro2.0YY-Sony A7R II
Sony A7S II« »YstereomonoYYmicro2.0YY-Sony A7S II

Both the 645Z and the A7R III are recent models that feature in their makers' current product line-up. The 645Z replaced the earlier Pentax 645D, while the A7R III followed on from the Sony A7R II.

Review summary: Pentax 645Z vs Sony A7R III

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.

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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).

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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 video autofocus: Features on-sensor phase-detection for more confident movie 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 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 (8000/sec vs 4000/sec) 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.
  • Sharper images: Has stabilization technology build-in to reduce the impact of hand-shake.
  • More legacy lens friendly: Can use many non-native lenses via adapters.
  • Faster data transfer: Supports a more advanced USB protocol (3.1 vs 3.0).
  • Easier file upload: Has wifi build 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.
  • 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 (20 : 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.

645Z 06:20 A7R III

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 handle or 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 rankings of the cameras as published by some of the major camera review sites (cameralabs, dpreview, ephotozine, imaging-resource, photographyblog). The full reviews are available by clicking on the site logo in the table header.

Review Scores
  Camera
Model
cameralabs dpreview ephotozine imaging-resource photographyblog Camera
Launch
(announced)
Launch
Price
(USD)
Street
Price
(USD)
Used
Price
(USD)
Camera
Model
Pentax 645Z»--4.5/55/55/5 Apr 2014 8,499 i i Pentax 645Z
Sony A7R III«HiRec90/1004.5/55/55/5 Oct 2017 3,199 i i Sony A7R III
Canon 1D X Mark II« »-89/1004.5/55/54.5/5 Feb 2016 5,999 i i Canon 1D X Mark II
Canon 5DS« »Rec83/1004.5/55/54.5/5 Feb 2015 3,699 i i Canon 5DS
Canon 5DS R« »Rec83/1005/55/54.5/5 Feb 2015 3,699 i i Canon 5DS R
Hasselblad X1D« »rev81/100--4/5 Jun 2016 8,995 i i Hasselblad X1D
Leica SL« »-84/1004.5/54/54/5 Oct 2015 7,450 i i Leica SL
Nikon D850« »HiRec89/1004.5/55/55/5 Jul 2017 3,299 i i Nikon D850
Nikon D5« »-89/1004.5/55/55/5 Jan 2016 6,499 i i Nikon D5
Nikon D7200« »HiRec84/1004.5/54/54.5/5 Mar 2015 1,199- i Nikon D7200
Nikon D4S« »--4.5/55/54.5/5 Feb 2014 6,499- i Nikon D4S
Pentax 645D« »---4.5/5- Mar 2010 9,995- i Pentax 645D
Sony A7 III« »HiRec89/1005/55/55/5 Feb 2018 1,999 i i Sony A7 III
Sony A9« »HiRec89/1005/55/55/5 Apr 2017 4,499 i i Sony A9
Sony A99 II« »-85/1004.5/54.5/54.5/5 Sep 2016 3,199 i i Sony A99 II
Sony A7R II« »HiRec90/1005/54.5/55/5 Jun 2015 3,199- i Sony A7R II
Sony A7S II« »Rec-4.5/55/55/5 Sep 2015 2,999 i i Sony A7S II

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. If you do not see the camera that you are looking for, kindly get in touch, and I will try to add information on that model to the database.

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